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SKEPTICISM – The Encyclopedia of Philosophy


Verbete da “” – Paul Edward, Editor in Chief. vol VII. Collier Macmillan Publishers, London.


SKEPTICISM, as a critical philosophical attitude, questions the reliability of the knowledge claims raised by philosophers and others. Originally the Creek term skeptikos meant "inquirers." Philosophical skeptics have been engaged in inquiry into alleged human achievements in different fields lo see if any knowledge has been or could be gained by them. They have questioned whether any-necessary or indubitable information can actually be gained about the real nature of things. Skeptics have organized their questioning into systematic sets of arguments aimed at raising doubts. Extreme skepticism questions all knowledge claims that go beyond immediate experience, except perhaps those of logic and mathematics. A limited or mitigated skepticism in different degrees questions particular types of knowledge claims made by theologians, metaphysicians, scientists, or mathematicians which go beyond experience, but it admits some limited probabilistic kinds of knowledge. Some skeptics have held that no knowledge beyond immediate experience is possible, while others have doubted whether even this much could definitely be known. The arguments advanced by skeptics from Greek times onward, and the use to which these arguments have been put, have helped to shape both the problems dealt with by the major Western philosophers and the solutions they have offered.


Skeptical tendencies appear in some pre-Socratic views. The metaphysical theory of Heraclitus that everything is in flux and that one can’t step twice into the same river was taken as indicating human inability to discover any fixed, immutable truth about reality. The purported development of this theory by Cratylus to the view that since everything is changing, one can’t step once into the same river, because both that river and oneself are changing, leads to a broader skepticism. Cratylus apparently became convinced that communication was impossible because, since the speaker, the auditor, and the words were changing, whatever meaning might have been intended by the words would be altered by the time they were heard. Therefore, Cratylus is supposed to have refused to discuss anything and only to have wiggled his finger when somebody said something, to indicate that lie had heard something but that it would be pointless to reply, since everything was changing.

Xenophanes questioned the existence of any criterion of true knowledge in his observation that if, by chance, a man came across the truth, be would be unable to distinguish it from error.

More serious skeptical doubts were raised by some of the Sophists. Gorgias is reported to have doubted whether anything exists, and to have offered an argument that if anything did happen to exist, we could not know it; and if we did know it, wc could not communicate it.

The relativism involved in the famous saying of the great Sophist Protagoras, "Man is the measure of all things," indicates another skeptical tendency. Plato’s discussion of Protagoras’ view shows that it was taken as a denial that there is absolutely true knowledge, and that each man’s views are equally valid versions of what is going on. No further standards of judgment exist.

Academic skepticism- Although Pyrrho, from whom the Pyrrhonians get their name, lived before the major Academic skeptics, skepticism as a philosophical methodology was first formulated by the leaders of Plato’s Academy in the third century’ B.C. Beginning with Arcesilaus (c. 315-c. 240 bc), the Academics rejected Plato’s metaphysical and mystical doctrines. Instead they concentrated on what they thought was involved in the Socratic remark "All that I know is that I know nothing," and on the questioning method and tactics of Socrates as portrayed in the Platonic dialogues. Although we do not possess the writings of Arcesilaus, or of the reputed greatest member of the school, Carneades (c. 213-128 B.C.), later writings by Cicero, Sextus Empiricus, and Diogenes Laertius give a fairly good idea of the kinds of arguments they developed. The attack of Arcesilaus was directed primarily against the Stoics, and that of Cameades against both#the Epicureans and Stoics. The Stoics had claimed that there were some perceptions which could not possibly be false either per se or as signs of the true nature of reality. Arcesilaus and Carneades pointed out that there was no criterion for distinguishing a perception of this kind from one that appeared to be so, or was thought to be so. Cameades insisted that there were no intrinsic marks or signs which these so-called real perceptions possessed and which illusory ones did not, and that no justifiable criterion existed for separating one type from the other. Therefore, he contended, we must suspend judgment about whether reliable representations of objects actually exist. This state of affairs, the Academics maintained, showed that no assertions about what is going on beyond our immediate experience are certain. The best data that we can acquire, they said, only tell us what is reasonable or probable, but not what is true. Carneades seems to have developed a verification theory and a probabilistic view resembling those of twentieth-century pragmatists and positivists. The view attributed to Carneades thus constituted a kind of mitigated skepticism.

The Academic skeptics dominated the Platonic Academy until the first century B.C., when, during the period that Cicero studied there, it was taken over by the eclectic philosophers Philo of Larissa and Antiochus of Ascalon. Cicero’s De Academica and De Natura Deorum describe both the traditional skeptical views and those of the newer teachers. St. Augustine’s Contra Academicos was an attempt to answer the skepticism described by Cicero.

The Pyrrhonian school. In the Roman period, the main center of skeptical activity shifted from the Academy to the Pyrrhonian school, probably connected with the methodic school of medicine at Alexandria. The Pyrrhonians attributed their origins to the views of Pyrrho of Elis (c. 360-c. 270 B.c;.). Pyrrho left no writings but was, rather, the model of the skeptical way of life. The stories about him indicate that he tried to avoid committing himself to doctrines about the nature of reality while living according to appearances and attempting to attain happiness, or at least peace of mind. His student Timon (c. 320-c. 230 B.C.) attacked a great many views, including those of the Academic skeptics, mainly by satire while developing a practical, moral way of living according to human necessities without making any grandiose commitments or claims.

Pyrrhonism, as a theoretical formulation of skepticism rather than merely an emulation of Pyrrho, is supposed to have begun with Aenesidemus, who probably taught in Alexandria in the first century B.C. He is reported to have attacked both the Academics and the dogmatic philosophers; the Academics because they were sure that what is probable and what is improbable are distinguishable, and the dogmatic philosophers because they thought they had discovered the truth. Aenesidemus and his successors, using the achievements of the Academics, developed "tropes," or ways of carrying on skeptical argumentation in order to produce epoche (suspension of judgment) about matters dealing with what is nonevident. The fullest presentation of this type of skepticism that we possess is that of Sextos Empiricus (second or third century), one of the last Pyrrhonian teachers. In his Pyrrhoniarum Hypotyposes and Advcrsus Mathematicos, Sextus set forth the Pyrrhonian tropes in groupings of ten, eight, five, and two, each set indicating why one should suspend judgment about all claims to knowledge extending beyond immediate experience. The most famous of these sets was the ten tropes (attributed to Aenesidemus). The first four of these ten deal with contradictions involved in trying to perceive the real nature of things. Animals’ perceive things differently; different men perceive things differently; man’s senses perceive the same object in various ways; and man’s circumstances also seem to alter what he perceives. Have we any way of being sure that man, and not some other animal, perceives the world correctly? And have we any way of telling which men, or which of our senses, or under what circumstances we are able to, perceive the true nature of things? Others of the ten tropes suggest that the object may be difficult or impossible to perceive correctly because it or our perceiving organs change or are affected by circumstances, frequency of occurrence, or customs of the society in which the observations take place.

In further analyses, Sextus brought forth Pyrrhonian arguments to cast doubt on any claims by dogmatic philosophers to have gained knowledge of the naturally nonevident world (that is, of any reality tnat is not now being, and cannot at some time be, observed). Any criterion, such as logical inference or presumed causal connection, used to judge what is naturally nonevident can be challenged by asking if the criterion itself is evident. The fact that there are disputes about everything that is not observable shows that it is not obvious what criterion should be adopted. The dogmatist is faced either with begging the question by using a questionable criterion to establish the standard of what is true, or with an infinite regress involving finding a criterion for judging his criterion, and a criterion for this, and so on. In attacking the various forms of the dogmatic claim to know what is nonevident, Sextus presented fully developed or in embryo almost all of the arguments to appear later in the history of skepticism. Sextus also presented a battery of Pyrrhonian arguments against the Stoic contention that there are indicative signs in experience that indubitably reveal what is the case beyond experience.

The point in all this argumentation, Sextus stated, was to lead mankind to the Pyrrhonian goal of ataraxia (unperturbedness). As long as people try to judge beyond appearances and to gain knowledge in the dogmatist’s Sense, they will be frustrated and worried. By setting forth the evidence pro and con, without even judging if it is good or satisfactory evidence, they will be led to suspension of judgment and peace of mind, and thereby will be cured of the dogmatist’s disease, rashness.

Sextus reported (he carefully avoided saying that he asserted anything) that the Pyrrhonians did not hold to the negative dogmatic conclusions of the Academics, in that they did not deny that knowledge of the nonevident was possible. Instead, they suspended judgment on the question. In response to opponents who tried to portray the Pyrrhonian attitude as a definite view, Sextus said that it was like a purge that eliminates everything, including itself.

The Pyrrhonians replied to the charge that their attitude would make living impossible by stating that they were not in any way doubting the world of appearances, and that one could live peacefully and undogmatieally in that world by following natural inclinations (without judging that they were right or wrong) and experience and what it suggests, in terms of patterns (what the Pyrrhonians called "suggestive signs") and the laws and customs of society.

The Pyrrhonian movement continued until the third century as both a philosophical and a medical one (medical skeptics cast doubt both on the claim that diseases have causes and on its denial). It questioned theories in physics, logic, mathematics, astrology, grammar, and other disciplines. The movement died out in the late Hellenistic period and had little influence thereafter as religious views became predominant.

The medieval period. As the Roman Empire became Christianized, the major remaining indication of skeptical influence was St. Augustine’s discussion of Academic skepticism. His Contra Academicos was the last major attempt before the Renaissance to come to grips with skeptical questions in epistemology. Augustine was strongly attracted to Cicero’s views and to the Platonism of the Middle Academy. Part of the resolution of his personal religious crisis was his realization, presented in Contra Academicos and other early writings, that skepticism can be completely overcome only by revelation. From this standpoint philosophy becomes faith  seeking understanding.

In the Christian Middle Ages it was mainly Augustine’s version of, and his answer to, skepticism that was discussed. Two medieval Latin translations of Sextus exist, one from the late thirteenth century and the other at least a century later, but there is no evidence that they were at all widely read or taken seriously.

 In the Islamic world, where there was more direct access to classical writings, there are more indications of skeptical currents, especially among the more extreme antirational Spanish Muslim and Jewish theologians. The arguments of al-Chazali and Yehuda Halevi against the possibility of rational scientific and theological knowledge about the real nature of the universe, and especially against the claims of the Aristotelians of the period, are often very’ similar to classical Academic and Pyrrhonian attacks. (And al-Ghazali’s skeptical rejection of rational knowledge of necessary connections in the world is very-close to that of Malebranche and Hume.) However, the use made of skepticism by Arabic and Jewish authors was radically different from that of the classical writers. Al-Ghaziili and Yelvuda Halevi were concerned to bring men to a mystical and nonrational appreciation of religious truths by making them see the intellectual bankruptcy of the rational theologies then current. Al-Ghazali’s great treatise that led to the end of the golden age of Islamic philosophy and science was entitled Autodestruction of the Philosophers. (This same type of view reappeared in the late Christian Middle Ages in Nicholas of Cusa’s theory of learned ignorance.)

Renaissance and Reformation. The rediscovery of the classical skeptical texts during the Renaissance vitally affected the development of modern thought. The writings of Sextus and Cicero’s De Academica began to arouse interest again. Present evidence indicates that the Greek text of Sextus, probably brought to Europe from Constantinople, was known in manuscript at least as early as 1441, and that various humanistic scholars used materials from Sextus. In 1562 Henri Estienne (Stephanus) published at Paris a Latin translation of the Pyrroniarum Hypotyposes, and in 1569 Gentian Hervet published a Latin translation of Adversus Mathematicos at Antwerp. The Greek texts were first printed at Cologne, Paris, and Geneva in 1621. There is also indication that some of Sextus’ works were translated into English in the 1590s, but this translation has not been found. A fragment from Sextus was later published as "The Skepticke," attributed to Sir Walter Raleigh. A complete English translation of the Hypotyposes appeared in Thomas Stanley’s History of Philosophy (4 vols., London, 1655-1662). A partial French translation was done by Samuel Sorbiere in the 1630s, but it was not published. Another unpublished French translation from the seventeenth century was discovered in a collection of manuscripts acquired by the University of California at Los Angeles. The first complete French translation, by Claude Huart, did not appear until 1725.

Religious controversy. At first Renaissance interest in both Academic and Pyrrhonian views appeared principally in theological discussions. Erasmus, in In Praise of Folly, after ridiculing various Scholastics, remarked that he preferred the Academics because they were "the least surly of the philosophers." Later, in his De Libero Arhitrio (Basel, 1524), attacking Luther’s view, Erasmus contended that the problem of free will was too complex for humans to comprehend, and Scripture too difficult to interpret on these matters. Therefore, he recommended the skeptical attitude of suspension of judgment, along with acceptance of the church’s view. Luther furiously attacked this skeptical defense of Catholicism in his De Sen;o Arbitrio (Wittenberg, 1525) and insisted that a Christian cannot be a skeptic; that he must be certain, not dubious, since salvation is at stake. Erasmus could remain a genial doubter if he wished, but Luther warned him that Judgment Day was to follow, and "Spiritus sanctus non est Scepticus."

In the dispute between Erasmus and Luther a fundamental problem that was to awaken a vital concern with skepticism was raised, the problem of determining the criterion of ultimate religious knowledge. At Leipzig, Luther had challenged the church’s criterion: that of the pope, the councils, and tradition. At the Diet of Worms he had proposed a subjective, private one instead, that of the dictates of the Holy Spirit to each man’s own conscience. The ensuing battle to justify either the church’s or the reformers’ criterion made this classical skeptical problem a living issue. The recently rediscovered texts ol Sextus, Cicero, and others played a major role in this battle. A skeptical crisis developed which modern philosophy would seek to resolve. Erasmus’ solution, that of suspending judgment and accepting the Catholic view on faith or tradition, was later developed into what is sometimes called Christian Pyrrhonism.

The new skepticism. At the outset of the sixteenth century Gian Francesco Pico della Mirandola (the nephew of the famous humanist) and Henricus Cornelius Agrippa von Nettesheim used the skeptical arguments to attack the Scholastics, the new Renaissance scientists, the alchemists, the cabalists, and others and, by undermining all confidence in man’s alleged rational achievements, to lead him to true religion. Renaissance changes in man’s conception of the cosmos further intensified the emerging skeptical crisis. Voyages of exploration and new astronomical theories and discoveries destroyed many of the medies’al beliefs about the nature and content of the cosmos. Reports of explorers concerning the superior moral character of savages cast doubt on previously accepted moral theories. The rediscovery of classical theories made many thinkers dubious about scholastic methods and conclusions. A wide spectrum of creative theories emanating from Iberia—cabalism, mysticism, and other doctrines— added to the unsettling ferment. Servetus and Vesalius revolutionized views about anatomy. Paracelsus challenged accepted medical theories and practices. The revival of interest in Hebrew, in Jewish views, and in early and deviant Christian theories raised still further problems. Most crucial of all, almost every accepted theological doctrine was now questioned, and a wide variety of other possibilities were offered.

In this atmosphere a series of new skeptical writings appeared. Some plainly and simply urged, because of the bankruptcy of human reason, acceptance of the wise conclusion of the ancient skeptics as well as acceptance of traditional religion. Pedro Valencia’s Academica (Antwerp, 1596) offered a survey of ancient skepticism, claiming it would make one realize that the Greek philosophers had not found the truth, and that one should turn away from the philosophers to God and recognize that Jesus is the only sage.

Hervel. Gentian Hervet, secretary to the Cardinal of Lorraine and a veteran of the Council of Trent, pointed out in the preface to his Latin translation of Sextus that the importance of this ancient work was its demonstration that human reason is incapable of opposing or resisting the arguments that can be raised against it. God’s revelation is our only source of certainty. Therefore, he contended, the arguments of Sextus provided a powerful answer to Calvinism. The Calvinists claimed to have a new theory about God. By showing that all human claims to knowledge are dubious, Hervet contended that those of Calvin are dubious as well. When man realized the vanity of all attempts to comprehend the universe, he would become humble and recognize that Cod can be known only by faith, not by the reasoning of the reformers. Hervet’s employment of Pyrrhonism against Calvinism was soon to be shaped into a skeptical machine of war for use by the Counter Reformation.

Sanches and Montaigne. The most philosophical statements of the new skepticism and its relevance to the problems of the day were offered by Michel de Montaigne and his distant cousin Francisco Sanches. Sanches (c. 1550-1623), an Iberian refugee from the Inquisition, taught philosophy and medicine at Toulouse. In his Quod Nihil Scitus, written in 1576 and published in 1581, he used the classical skeptical arguments to show that science, in the Aristotelian sense of giving necessary reasons or causes for the behavior of nature, cannot be attained. He then argued that even his own notion of science-perfect knowledge of an individual thing—is beyond human capabilities because of the nature of objects and the nature  of man.  The interrelation of objects, their

unlimited number, and their ever-changing character prevent their being known. The limitations and variability of man’s senses restrict him to knowledge of appearances, never of real substances.

Sanches’ first conclusion was the usual fideistic one of the time, that truth can be gained only by faith. His second conclusion was to play an important role in later thought: just because nothing can be known in an ultimate sense, we should not abandon all attempts at knowledge but should try to gain what knowledge we can, namely, limited, imperfect knowledge of some of those things which we become acquainted with through observation, experience, and judgment. The realization that nihil scitur ("nothing is known") thus can yield some constructive results. This early formulation of "constructive" or "mitigated" skepticism new to be developed into an important explication of the new science by Marin Mersenae, Pierre Gassendi, and the leaders of the Royal Society.

The most influential version of the new skepticism in setting the problems for modern philosophy was Montaigne’s. His rambling essay Apologie de Haimond Scbond, written shortly after he read Sextus and went through his own personal crise pyrrhonienne, summed up the skeptical currents of the sixteenth century and showed why all of man’s rational achievements up to that point were seriously in doubt. Starting from a quibble about the validity of the arguments of the fifteenth-century Spanish theologian Sebond (Raymond de Sabunde), Montaigne moved to a general skeptical critique of the possibility of human beings understanding anything. He kept repeating that only through faith and revelation can real knowledge be gained. Montaigne used a vast variety of ancient skeptical arguments, often modernizd by new examples. He stressed the skeptical difficulties involved in judging the reliability of sense experience. He pointed out the personal, social, and cultural factors that influence people’s judgments. And he showed that the criteria employed to determine standards of judgment are themselves open to question and doubt, unless Cod gives us some indubitable first principles and makes our faculties reliable- Unaided by divine grace, all of man’s achievements, even those of the most recent scientists, become dubious. All we can do, Montaigne asserted, is follow the Pyrrhonian suspension of judgment, live according to nature and custom, and accept what God chooses to reveal to us.

The seventeenth century. Montaigne’s skepticism, both as set forth in the Apologie and in the more didactic presentations of his disciples, Pierre Charron’s De la Sagesse (Bordeaux, 1601) and Jean-Pierre Camus’ Essay sceptique (Paris, 1603), became most popular in the early seventeenth century, especially among the avant-garde intellectuals in Paris. The so-called libertins, including Gabriel Naude, Mazarin’s secretary; Guy Patin, rector of the Sor-bonne medical school; and Francois de La Mothe Le Vayer, teacher of the dauphin, espoused Montaigne’s attitude and were often accused of being skeptical even of fundamental religious tenets. Others, like Francois Veron, used the arguments of Sextus and Montaigne to challenge the Calvinist claim of gaining true knowledge from reading Scripture. Counter Reformers, by raising skeptical episte-mological problems about whether one could determine what book is the Bible, what it actually says, what it means, and so on, forced Calvinists to seek an indisputable basic for knowledge as a prelude to defending their theological views.

Gassendi and Mersenne. Perhaps the most forceful presentation of skepticism in the early seventeenth century is Pierre Gassendi’s earliest work, Exercitationes Para-doxicae Adversus Aristoteles (Grenoble. 1624). Gassendi challenged almost every aspect of Aristotle’s view, is well as many other theories. He applied a battery of ancient and Renaissance skeptical arguments, including that "No science is possible, least of all in Aristotle’s sense." In this work Gassendi indicated in embryo what became his and Marin Mersenne’s constructive solution to the skeptical crisis, the development of an empirical study of the world of appearances rather than an attempt to discover the real nature of things.

In the 1620s works challenging the prevalent skeptical tendencies began to appear. Some authors simply stated that Aristotle would have resolved the difficulties by-applying his theory of sense perception and knowledge to the problems raised. Others, like Francois Garasse, decried the irreligious tendencies they discerned in all this doubting. Still others, like Francis Bacon, tried to overcome the skeptical difficulties by appealing to new methods and new instruments that might correct errors and yield firm and unquestionable results. Herbert of Cher-bury, in De Veritate (1624), offered an elaborate scheme for overcoming skepticism which combined Aristotelian and Stoic elements, and ultimately appealed to common notions, or truths known by all men, as the criteria by which reliable and indubitable judgment would be possible. Mersenne, in many writings of the 1620s and 1630s, used skeptical materials (as did Gassendi) to attack the alchemists, the cabalists, and other Renaissance pseudo scientists, and he tried to mitigate the force of the skeptical challenge by pointing out how, in fact, worthwhile "knowledge" is gained. Mersenne granted that the problems raised by Sextus could not be answered and that, in a fundamental sense, knowledge of the real nature of things cannot be attained. However, he insisted, information about appearances and deductions from hypotheses can provide an adequate guide for living in this world and can be checked by verifying predictions about future experiences. Gassendi, in his later works, developed this constructive skepticism as a via media between complete doubt and dogmatism, and offered his atomic theory as the best hypothetical model for interpreting experience. Mersenne and Gassendi thus combined skepticism about metaphysical knowledge of reality with a way of gaining useful information about experience through a pragmatic scientific method.

Descartes. Rene Descartes, raised in the skeptical atmosphere of early seventeenth-century France, insisted that it was possible to overcome all doubt and to find an absolutely certain basis for knowledge. By applying the skeptical method more thoroughly than the skeptics had, he claimed, an indubitable truth, as well as an indubitable criterion of true knowledge and a whole system of truths about reality, could be found. Descartes started by rejecting all beliefs rendered dubious by the skeptical problems about sense experience, the possibility that all that we know is part of a dream (a theory’ ‘hat appeared in Gicero and Montaigne), and the possibility that there may be a demon who distorts our judgment (a new skeptical possibility which he introduced). In the process of trying to doubt everything, Descartes claimed, one basic indubitable truth—"I think, therefore I am"—is encountered. The very act of doubting one’s own existence makes one aware of the truth that one exists. By examining what characteristics make this truth indubitable, the criterion of true knowledge, that whatever ideas are clearly and distinctly perceived are true, is discovered. This criterion then enables one to find true first principles among one’s ideas and to use these principles to prove that there is a God, that God is not a deceiver, that he guarantees that whatever we clearly and distinctly perceive really is true, and that there is an external world. The Cartesian "way of ideas," then, takes skepticism as its point of departure, uses it to reveal a basis of certitude, and then further uses it to gain indubitable metaphysical knowledge from our clear and distinct ideas.

Replies to Descartes. Descartes’s dramatic resolution of the skeptical crisis generated a new era of skeptical argumentation. The skeptics sought to show that Descartes had not really conquered skepticism, while his dogmatic opponents tried to show that he was actually a skeptic in spite of himself. To refute Descartes, traditional skeptical arguments had to be refashioned and redirected. In the objections to Descartes’s Meditations (Paris, 1641), Gassendi, Mersenne, and others argued that either fundamental skeptical difficulties remained in the Cartesian system or that Descartes had not really established anything absolutely certain. During the rest of the seventeenth century skeptical challenges were raised about what, if anything, had actually been proved by the cogito, about whether Descartes’s criterion was of any value, and about whether the "truths" Descartes enunciated about the mathematical-physical universe were actually certain or ever true. Gassendi, and later Pierre-Daniel Huet, charged that cither the cogito stated an uninteresting truism or it was fraught with problems. Huet’s Censura Philosophae Car-tesiana (Paris, 1689) and his unpublished defense of it raised doubts about each element of the proposition "I think, therefore I am" until it became "I may have thought, therefore perhaps I may be." Gassendi, Huet, and others questioned whether Descartes’s criterion could determine what was true or false. Could we really tell what was clear and distinct, or could we only tell that something appeared clear and distinct to us? Would we then need another criterion to tell when the first actually applied, and so on? Mersenne pointed out that even with the criterion we could not be sure that what was clear and distinct to us, and hence true, was really true for God. Hence, in an ultimate sense, even the most certain Cartesian knowledge might be false. Gassendi, in what Descartes called "the objection of objections," pointed out that for all anyone could ascertain, the whole Cartesian system of truths might be only a subjective vision in somebody’s mind and not a true picture of reality. Huet argued that since all the fundamental Cartesian data consisted of ideas, and ideas are not real physical things, the Cartesian world of ideas, even if clear and distinct, cannot represent something quite different from itself.

Followers of Descartes. As Cartesianism was attacked from many sides, adherents modified it in various ways. The radical revision of Nicolas Malebranche, designed partially to avoid skeptical difficulties involved in connecting the world of ideas with reality, was immediately attacked by the skeptic Simon Foucher. The orthodox Cartesian Antoine Arnauld claimed that Malebranchism could only lead to a most dangerous Pyrrhonism. Foucher, who wished to revive Academic skepticism, applied various skeptical gambits to Malebranche’s theory, one of which was to be important in subsequent philosophy. He argued that the skeptical difficulties which Descartes and Malebranche used to deny that sense qualities (the so-called secondary qualities—color, sound, heat, taste, smell) were features of real objects, applied as well to the mathematically describable primary qualities like extension and motion, which the Cartesians considered the fundamental properties of things. These mathematical qualities, as perceived, are as variable and as subjective as the others. If the skeptical arguments are sufficient to cause doubt about the ontological status of secondary qualities, Foucher contended, they are also sufficient to lead us to doubt that primary ones are genuine features of reality.

English skepticism. While the French skeptics were busily challenging the new dogmatism of Descartes, in England a somewhat different kind of skepticism was developing. As a result of theological controversies, some Anglican writers, starting with William Chillingworth, tried to distinguish unanswerable, hyperbolic, and metaphysical doubts, of the sort raised by Sextos and Descartes, from reasonable ones that could be dealt with in terms of probabilities and common sense. They pointed out that absolutely certain knowledge about the world is unattainable. However, there is information that can be called knowledge in the sense that it cannot reasonably be doubted. Bishop John Wilkins and Joseph Glanvill, two early members of the Royal Society, distinguished between infallibly certain and indubitably certain knowledge. Infallibly certain knowledge cannot be attained by human beings because their faculties may be corrupt or defective, and any of the necessary connections they think they discover in the world may be mere concomitancies which could be otherwise. However, in ordinary life there are many indubitable beliefs that no reasonable man questions. In terms of this distinction Wilkins, Glanvill, and their colleagues built up a theory of empirical science and jurisprudence for studying nature and deciding human problems within the limits of "reasonable doubt." Their limited skepticism appears in the Anglo-American theory’ of legal evidence and in the theory of legal evidence and in the theory of science of the early Royal Society. They believed that by applying their probabilistic empirical method to religious questions they could justify a tolerant, latitudinarian form of Christianity. John Locke to some extent followed their views in rejecting total skepticism as unreasonable and in appealing to common-sense standards to answer or avoid traditional skeptical difficulties.

Other resolutions of skepticism. Other, answers were offered to the skeptics and to their challenge of some of the basic tenets of the new philosophy. Hobbes had admitted the force of the problem of finding the criterion forejudging what was genuinely true, and he insisted that the solution was ultimately political—the sovereign would have to decide. Pascal in his scientific works gave one of the fines! expositions of the hypothetical probabilistic nature of science and mathematics. In his Pensees he stated the case for ultimate and complete skepticism as strongly as it ever has been done. But, he contended, no matter how much reason leads us to doubt, "I lay it down as a fact that there never has been a real complete skeptic. Nature sustains our feeble reason, and prevents it raving to this extent." (Arnauld, in the Port-Royal Logic, similarly called the Pyrrhonists a sect of liars, since they could not believe what they said.) Pascal portrayed man as both a natural and instinctive believer and "a sink of uncertainty and error." His solution lay in turning to God, not in any philosophical answer. Spinoza, on the other hand, with his completely rational vision of the world, could not regard skepticism as a serious problem. If one had clear and adequate ideas, there would be no need or excuse for doubting. Doubt was only an indication of lack of clarity, not of basic philosophical difficulties.

The philosopher who took the skeptics most seriously was Leibniz, a close friend of Huet and Foucher and a correspondent of Pierre Bayle’s. Many of Leibniz’ most famous statements of his views are answers to these skeptics. Leibniz believed that his system of logic, epistemol-ogy, and metaphysics was impervious to their criticisms. Foucher tried to show him that he failed to take seriously the skeptical challenge to the very principles of reasoning that he employed and to the traditional assumptions about the nature of knowledge that he accepted. Bayle, in the article "Rorarius" in his Dictionnaire historique et critique, offered the first major critique of Leibniz’ theory of the pre-established harmony, showing it had been no more successful in resolving skeptical difficulties than had previous metaphysical systems and was at least as implausible as the others.

Bayle and the Enlightenment. At the end of a century of attempts to deal with the skeptical crisis, perhaps the most incisive of the modern skeptics, Pierre Bayle, summed up the seventeenth-century intellectual situation in his monumental Dictionnaire historique et critique (2 vols., Rotterdam, 1697-1702), in which he opposed "everything that is said and everything that is done." Bayle’s Dictionnaire is biographical, and most of the important discussion occurs in long, digressive footnotes to lives of often very insignificant figures. Bayle was a master dialectician who delighted in offering skeptical challenges to philosophical and theological theories, ancient or modern, from Thales to Leibniz, Locke, and Newton. Using all the gambits of the skeptical tradition, Bayle sought to show that most theories "are big with contradiction and absurdity" and that man’s efforts to comprehend the world in rational terms always end in perplexities, bewilderment, and insoluble difficulties. He thereby developed a most extreme skepticism, questioning the knowledge claims of theology, metaphysics, mathematics, and the sciences. In notes B and C to his article "Pyrrho," and in his clarification of the article in the Appendix, Bayle argued that the new philosophy cast all in doubt. It had started from the doubts of Sextus Empiricus, and in spite of Descartes’s efforts and those of his successors, it was ending in a complete skeptical debacle. Using Foucher’s argument and some ammunition from Malebranche, Bayle contended that the doubts accepted by modern philosophers about the real external existence of secondary qualities applied to the primary ones as well, so that we cannot tell what characteristics the external world might have, nor even if there is one.

Gassendi and Huet had challenged whether the Cartesian criterion could ever be successfully applied. Bayle challenged whether it was even the criterion of knowledge. He argued for the possibility of a proposition’s being clear and distinct and yet demonstratively false. (Many theologians and philosophers tried to refute this challenge by showing that rational discourse would be destroyed if no standards existed.)

The point of his skeptical attack, Bayle insisted, was to make men see that philosophy was an unsatisfactory’ guide and could only lead to doubts. Then, perhaps, they would abandon reason and turn to faith. Bayle’s presentation of what this turn to faith involves has none of the fervor of Pascal. It usually seems to be just a tepid statement of the unintelligibility and amorality of a faith that is to be accepted blindly. What he himself believed is almost impossible to determine in the morass of doubts. Bayle also employed his skepticism as a justification for complete toleration. If all theories about the ultimate nature of reality are questionable, can there be any basis for persecuting people for accepting one rather than another? People accept views on the basis of what their consciences force them to believe. An erring conscience would have the same effect as a correct one in compelling assent. Since right or true belief cannot be distinguished from false ones, there is no justification for persecuting people for their beliefs.

Bayle’s Dictionnaire was the coup) de grace to the seventeenth century’s attempt to find a new metaphysical basis for certain knowledge. Among major philosophers, only George Berkeley thought the skeptical crisis could still be resolved through another metaphysical scheme. By denying the ontological distinction between ideas and things, and thereby removing the basis for many of the skeptical arguments, Berkeley thought he could refute the skeptics and establish the reality of human knowledge. To his chagrin, he was soon classed as just one more ingenious skeptic, as well as a visionary with a strange spiritualistic metaphysics. Almost everyone else seemed willing to accept Bayle’s demolishing of the quest for metaphysical certainty. His skeptical arguments were soon applied to traditional religion by Voltaire and others. But in place of Bayle’s doubts or his appeal to faith, they offered a new way of understanding man’s world—that of Newtonian science—and professed an inordinate optimism about what man could comprehend and accomplish through scientific examination and induction. Though Bayle remained the heroic figure who had launched the Age of Reason by criticizing all the superstitions of past philosophy and theology, the leaders of the Enlightenment, both in France and in the British Isles, felt that his skepticism was passe and only represented the summit of human understanding before "God said. Let Newton be, and all was light." Various simple answers were now offered to skepticism, some by the Scottish moral theorists and some by overzealous dogmatists like Jean Pierre de Crousaz, who accused skepticism of being responsible for everything evil, including even financial crises.

Hume. In the euphoric intellectual atmosphere of the eighteenth century, still worried about skepticism. An avid reader of Bayle, Hume seems to have lived through his own personal skeptical crisis as ho wrote his A Treatise of Human Nature. Hume sometimes held a most extreme skeptical position, going at least as far as Bayle in questioning even the knowledge claims of science, mathematics, and logical reasoning, and sometimes held a limited, mitigated skepticism allowing for probabilistic standards for evaluating beliefs about what is beyond immediate experience. When Hume examined the general nature of all beliefs, he tended toward complete skepticism. When he examined metaphysics and theology, in contrast with science, he tended toward a positivistic, limited skepticism. And when he developed his own views about human nature and conduct, his doubts tended to recede and his positive views became more pronounced.

Hume had a Newtonian vision that if the "experimental method of reasoning" were applied to moral subjects, the character of man’s intellectual endeavors would be clarified and the limits of human capacities would be made apparent. The enthusiasm of Hume’s Preface indicates his optimism about constructing "a science of man." His analysis revealed a skepticism about man’s ability to gain knowledge about anything beyond the immediately obvious or demonstrable relationships of his ideas. In the course of the Treatise and the Enquiry Concerning Human Understanding, Hume showed that no truths about matters of fact could be established deductively or inductively. Since any conceivable (imaginable) state of affairs is possible, Hume argued that no genuine demonstrative evidence could establish that something must be, and could not be otherwise. Inductive reasoning, Hume pointed out, is inconclusive, since its evidential value rests upon the assumption that nature is uniform, that the future will resemble the past. This assumption cannot itself be justified. Our information about the world beyond what is immediately perceived, except for "forced" beliefs, is the result of causal reasoning from a present impression to its supposed cause or effect. In analyzing such "reasoning," Hume showed that we are unable to discover any necessary connections among experienced events or any justifiable basis for applying data about the constant conjunctions of past events to future ones. When we examine why we believe that certain relationships exist between matters of fact, we see that customs or habits, rather than rational evidence, lead us to the views we hold. The quest for a justifiable basis for belief always reveals how unjustified are our beliefs about matters not immediately experienced. In Book I, Part IV of the Treatise, the last chapter of the Enquiry, and the Dialogues Concerning Natural Religion Hume undermined the reliability of rational and empirical arguments in philosophy and theology, and raised doubts concerning the merits of logical argumentation about the existence of an external world, of the self, and of God.

When we examine what we believe and what leads us to believe it, we find that "Philosophy would render us entirely Pyrrhonian, were not Nature too strong for it." The skeptical problems notwithstanding, we are naturally constrained to believe all sorts of things. Under normal conditions we find that we are led by nature to believe that the future course of events will resemble the past course, and on this we base our so-called "reasonable" or "scientific" views and expectations about the world. But nature does not refute complete skepticism. It only prevents us from believing in, or accepting, the doubts that result from skeptical reasonings.

Hume showed that man was caught between a total Pyrrhonism that he could not refute and a natural compulsion to believe in the future course of events, the reality of an external world, the existence of some kind of personal identity, and possibly in some kind of intelligent force in the world. These metaphysical and theological views were indefensible but unavoidable. The Hurnean skeptic could only accept the situation and explore, the reasons for doubting when he felt inclined to, at other times accepting what he found he had to believe. In a sense, Hume’s skepticism was a more consistent and forceful statement of the. original Pyrrhonian view. Though less detailed and thorough than Bayle’s dialectical demolishment of a wide variety of knowledge claims, Hume’s version centered the skeptical attack on the issues that were to dominate subsequent philosophy—the problems of induction, causality, external existence, the nature of the self, and the proofs of the existence of God. And Hume showed what was actually involved in the Pyrrhonian statement that the skeptic accepts beliefs by habit and custom, and according to nature. The skeptic could not suspend judgment on all questions without going mad, since "Nature, by an absolute and uncontrolable necessity has determin’d us to judge as well as to breathe and feel" (Treatise of Human Nature, Book I, Part 4, Sec. 1). More than any of his predecessors, Hume explored the nature of beliefs and the factors that induce people to accept them.

Reid and the common-sense school. In an era when most of his philosophical contemporaries were overly optimistic about human capabilities to comprehend the world, Hume’s skepticism was largely ignored, while his psychological, historical, political, and antireligious works were taken as a great contribution to the Age of Reason. One of the first to appreciate Hume’s skeptical arguments was Thomas Reid, who studied Hume’s writings for 25 years before publishing his answer. Inquiry into the Human Mind on the Principles of Common Sense (Edinburgh, 1764). Reid discerned that both Berkeley and Hume had shown that the basic principles of modern philosophy led systematically to total skepticism about man’s ability to attain any certainty or even probability about the world. The answer to this development, Reid contended, was not to ignore or scoff at the arguments of Berkeley and Hume but to reconsider the assumptions on which modem philosophy is based. When the conclusions of philosophy run counter to common sense, there must be something wrong with philosophy. Since nobody could believe and act by complete skepticism, the fact that this skepticism was the consistent issue of the Cartesian and Lockean way of ideas only showed the need to start anew. Reid offered his common-sense realism as a way of avoiding Hume’s skepticism by employing as basic principles the beliefs we arc psychologically unable to doubt.

Hume was unimpressed by Reid’s argument Reid, he believed, had seen the problem but actually had only offered Hume’s own solution, that nature does not allow us to live as if all were in doubt, even though we are unable to resolve all doubts theoretically. The Scottish common-sense school of Oswald, Beattie, Stewart, Brown, and others kept reiterating its claim to having refuted Hume’s skepticism by appealing to natural belief, while at the same time conceding that Hume’s fundamental arguments could not be answered. Thomas Brown, an early nineteenth-century’ disciple of Reid, admitted that Reid and Hume differed more in words than in opinions, saying, "’Yes. Reid bawled out, ‘we must believe in an outward world’; but added in a whisper, ‘we can give no reason for our belief.’ Hume cries out, ‘we can give no reason for such a notion’; and whispers, ‘I own we cannot get rid of it" (Sir James Mackintosh, Dissertation on the Progress of Ethical Philosophy, 2d ed., Edinburgh, 1837, p. 346).

The German Enlightenment and Kant. The Scottish school was perhaps the first to make Hume’s version of modem skepticism the central view to be combated if philosophy was to make coherent sense of man’s universe. The more fundamental attempt, for subsequent philosophy, to deal with Hume’s skepticism was developed in Germany in the second half of the eighteenth century and culminated in Kant’s critical philosophy. Such leaders of the Prussian Academy as Jean Henry Samuel Formey. Johann Bernhard Merian, and Johann Georg Sulzer had long been arguing against Pyrrhonism. They were among the first to read, translate (into French and German), and criticize Hume’s writings. They saw in the skeptical tradition up to Bayle and Huet, and in Hume’s version of it, a major challenge to all man’s intellectual achievements Although their answers to skepticism were hardly equal to the threat they saw in it, these writers helped revive intercst in and concern with skepticism in an age that thought it had solved, or was about to solve, all problems Others in Germany contributed to an awareness of the force of skepticism: Johmn Ghristoff Eschenbafch by his edition of the arguments of Sextus, Berkeley, and Arthur Collier, Berkeley’s contemporary, against knowledge of an external corporeal world; Ernst Plainer by his skeptical aphorisms and his German edition of Hume’s Dialogues on Natural Religion (1781); hosts of German professors by dissertations against skepticism; and the translators of the Scottish critics of Hume.

The culmination of this German concern with skepticism occurred when Kant was awakened from his dogmatic slumbers by reading Hume and his opponents- Kant save that Hume had fundamentally challenged the Enlightenment hope that all skeptical disputes could be settled by what Locke had called "the physiology of the understanding." and that the question "How is knowledge possible? had to be re-examined. Kant’s solution can be considered as an attempt to establish a middle ground inoorporating complete skepticism about metaphysical knowledge and a conviction that universal and necessarily certain knowledge existed about the conditions of all possible experience. He assumed that knowledge is possible, and hence that total skepticism is false. The problem was then to explain how this universal and necessary information could be attained, in the face of Hume’s arguments. In the view that knowledge begins with experience, but does not come from it, Kant believed he had found a revolutionary new answer to the skeptical crisis. Space and time are the necessary forms of all possible experience, and the categories and the logical forms of judgment are the conditions of all knowledge about experience. Mathematical knowledge is possible because it is not derived by induction from experience but is the way the world must be experienced, A science of nature is possible because all experience must be ordered and organized according to certain categories.

By transcendental analysis we can uncover the universal and necessary conditions imposed on all experience and judgment. But these conditions provide no means for gaining knowledge either about the contents of experience (as opposed to its form) or about what transcends experience, a supposed real world, a self, and God. The contents of experience can be learned only empirically and inductively, and such information is only probable. Metaphysical knowledge cannot be attained, since there is no way of telling if the conditions of experience apply beyond the limits of all possible experience, and no way of telling what to apply them to.

Skeptical rejoinders to Kant. Kant and his disciple Karl Friedrich Staudlin (who wrote the first systematic history of skepticism, from Pyrrho to Kant) regarded Kant’s critical philosophy as the finale of man’s long struggle with skepticism. Kant’s contemporaries and successors, however, saw his effort as beginning a new phase in skeptical thought and providing a new road to Pyrrhonism. From three different sides Kant was attacked by skeptical critics, each employing a portion of the earlier skeptical tradition as a way of showing that Kant had failed to resolve the skeptical crisis. G. E. Schulze (also known as Aenesidemus-Schulze, after the title of his major work of 1792) argued that Kant had not succeeded in establishing any genuine truths about objective reality, since as Kant himself had shown, there is no way of extending information about the conditions of thought to real objects, or things-in-themselves. But without any such extension, the objective validity of our judgments cannot be determined. At best, all that can be established is the subjective necessity of certain of our views, which is essentially what Hume had shown. So Schulze, by insisting on the inability of the Kantian analysis to move from subjective data about what people have to believe to any objective claims about reality, contended that Kant had not advanced beyond Hume’s skepticism, and that this failure of the Kantian revolution actually constituted a vindication of Hume’s views.

Salomon Maimon challenged Kant’s theory from within and developed a view which he called "rational skepticism." In contrast with Hume, Maimon agreed with Kant that there were rational a priori concepts, such as those involved in mathematics. In opposition to Kant, Maimon held that the applicability of transcendental concepts to experience w-as itself something based on inductions from experience. Since such inductions could only be universal and necessary knowledge about experience could be gained. Kant had assumed that such knowledge existed, and examined how this was possible. Maimon asked whether it was, and showed that the evidence was always experiential. Inductively it might become more and more probable that a priori concepts applied to experience, but, because of Hume’s critique of induction, we must remain skeptical on this score. Maimon ruled out metaphysical knowledge as unattainable, on both Humean and Kantian grounds.

Thus Maimon developed a mitigated Kantianism (to some extent like that of the Neo-Kantian movement a century later) in which the reality of a priori forms of thought is granted but in which the relation of these forms to matters of fact is always in question. Knowledge (that is, propositions that are universal and necessary, rather than ones that are just psychologically indubitable) is possible in mathematics but not in sciences dealing with the world. Unlike the logical positivists, who were to claim that mathematics was true because it consisted only of vacuous logical tautologies, Maimon contended that mathematics was true because it was about creations of our mind. Its objective relevance was always problematical. This turn to human creativity as the basis of truth was soon to be expanded by Fichte as a new road to knowledge of reality and a means of transcending skepticism.

Maimon’s partial skepticism exposed some of the fundamental limitations of Kant’s critical philosophy as a solution to the skeptical crisis. Another skeptical critique was offered by the religious thinker Johann Georg Hamann, who accepted Hume’s and Kant’s arguments as evidence that knowledge of reality cannot be gained by rational means but only by faith. Hamann exploited the skeptical thought of these philosophies to press for a complete anti-rational fideism. He used Hume’s analyses of miracles and of the evidence for religious knowledge to try to convince Kant of the futility of the search for truth by rational means. During the height of nineteenth-century positivism, materialism, and idealism, Hamann’s type of fideism was revitalized by Kierkegaard and Lamennais, who used it as a critique of French liberal, empirical, and Enlightenment views and as a new defense of orthodoxy and political conservatism. Kierkegaard brilliantly combined themes from Sextos, Hume, and Hamann to attack the rationalism of the Hegelians, to develop 3 thoroughgoing skepticism about rational achievements, and to show the need for faith in opposition to reason. Fideism has become a major element in twentieth-century neo-orthodox and existentialist theology, which tries to show that the traditional skeptical problems still prevent us from finding an ultimate basis for our beliefs except by faith.

Idealism. In the mainstream of philosophy after Kant, although skepticism continues to play a vital role, few philosophers have been willing to call themselves skeptics. The German metaphysicians, from Fichte and Hegel onward, sought to escape from the skeptical impasse produced by Hume and Kant and to reach knowledge of reality through the creative process and the recognition of historical development They attempted to portray skepticism as a stage in the awareness and understanding of the process of events. For Fichte skepticism made one recognize the need for commitment to a fundamental outlook about the world. The commitment to see the world in terms of creative thought processes led to a revelation of the structure of the universe as an aspect of the Absolute Ego.

For Hegel skepticism was the nadir of philosophy, actually its antithesis. According to Hegel, human knowledge is a historically developing process. At each stage of the process both our knowledge and the world itself arc limited and contain contradictions, which are overcome at the next stage. Only the final, Absolute stage, when no further contradictions can be developed, permits genuine knowledge that is not partly true and partly false. Then, presumably, skepticism is no longer possible. The English Hegelian F. H. Bradley, in his Appearance and Reality (London, 1893), used the traditional skeptical arguments to show that the world was unintelligible in terms of empirical or materialistic categories, and hence that one had to go beyond the world appearance to find true knowledge.

Recent assimilation of skepticism. The empirical and positivistic critique of speculative metaphysics, launched in the late nineteenth and early twentieth centuries by Ernst Mach, Bertrand Russell, Rudolf Carnap, and others, included a skepticism about the possibility of any metaphysical knowledge (amounting in some formulations almost to the Academic skeptical view that no knowledge beyond appearances is possible). Logical positivism and the later linguistic philosophy have tried to obviate the skeptical problems by restricting the use of the term "knowledge" to logically true tautologies, empirically verifiable facts, or ordinary common-sense beliefs and assertions. Similarly, pragmatists from William James onward have sought to eliminate skeptical difficulties by limiting the meaning of "true knowledge" to hypotheses that are pragmatically confirmed or verified. In such views, metaphysical assertions are no longer ranked as false or dubious but as nonsense, or non-assertions. They can be evaluated as poetic utterances, or appreciated for their emotive qualities, but they have no truth value.

Many other major views of the. last hundred years, whether intentionally or not, have included or taken for granted various aspects of traditional skepticism. Empiricists, from John Stuart Mill onward, have not claimed to have found any means of attaining certain knowledge beyond the world of experience or appearance, except in terms of logical and/or mathematical tautologies. And the information about the world of experience, they have granted, is only probable. The sciences have systematized our understanding of these data but have not thereby shown that they arc necessarily true. On the contrary, the probabilistic nature of science has been used by Russell and others as a constant warning against various dogmatic views. Russell, in his discussions of induction, has repeatedly stressed the logical force of the arguments offered to develop an extreme or complete skepticism.

James, Sigmund Freud, Karl Mannheim, and Charles Beard, while they have provided much insight into why we hold the views we do, have at the same time spawned newer forms of relativistic skepticism. By revealing the economic, social, and psychological factors that have led us to our beliefs, they have made it difficult, if not impossible, for us to consider the truth of what we believe apart from how or why we believe it. Truths, in the views of these writers, become relative to the person holding them and to the conditions under which they are held, rather than absolute assertions about the nature of things.

In a world in which most thinkers are covertly skeptical about the possibility of attaining knowledge concerning reality, there have been few overt skeptics recently. Since for many the impasse reached by Humean and Kantian thought is taken as the end of the quest for certain knowledge of reality, the skeptical problems seem out-of-date and irrelevant. When they are transferred from their original locus into questions about experience or common-sense belief, they appear odd and sometimes easily answerable, although these are hardly the same problems. The continuing appearance of refutations of skepticism by contemporary philosophers indicates, perhaps, that to some extent they are still haunted by the problems that no longer seem soluble.

Recent skeptics. Besides those contemporary fideists who employ skepticism as a road to religious faith, one might include as overt skeptics among twentieth-century thinkers such diverse figures as Fritz Mauthner, George Santayana, and Albert Camus, and as quasi skeptics figures like Hans Vaihinger, Alain, and possibly Karl Popper. Mauthner, in the early part of the century, developed a type of skepticism from his work on the analysis of language. Any language, he contended, is both social and individual, and shows only what linguistic conventions are used at given times and what features of experience they name in various ways. Each language expresses a Weltanschauung, and what is considered as true in a language is always relative to this outlook. When one attempts to ascertain what is true, one is thrown back on data about linguistic conventions and cannot proceed to any independent evaluation of the actual correspondence of assertions to objective states oi affairs.

Mauthner’s critique of language led him into complete skepticism about the possibility of genuine knowledge. Even his critique, he realized, was an attempt "to say the unsayable," and thus silent mystic contemplation was all that was really possible. In the light of his studies of atheism and religion, Mauthner called himself a "godless" mystic; "godless" because, according to his critique of language, "God" was as unwarranted a substantive name as any other.

A kind of naturalistic skepticism was offered by George Santayana, expecially in his Scepticism and Animal Faith (New York, 1923). Santayana insisted that "nothing given exists as it is given," and that all our beliefs about what is given are open to question. He contended that he was carrying skepticism further than Hume, had, in that he questioned both Hume’s description of what is given and his psychological interpretations of experience.

When the full force of complete skepticism is realized, Santayana claimed, one can appreciate what is in fact absolutely indubitable, the immediately experienced or intuited qualities that Santayana called "essences." The interpretation of these essences leads to various questionable metaphysical systems. A thoroughgoing skepticism makes one realize the unjustifiable assumptions involved in interpreting the realm of essences, and also that we do 

interpret them and thereby construct meaningful pictures of the world- Santayana called the process of interpretation "animal faith," which is consistent with complete skepticism and involves following natural and social tendencies and inclinations.

I have imitated the Creek sceptics in calling doubtful everything that, in spite of common sense, anyone can possibly doubt. But since life and even discussion forces me to break away from a complete scepticism, I have determined not to do so surreptitiously nor at random, ignominiously taking cover now behind one prejudice and now behind another. Instead, I have frankly taken nature by the hand, accepting as ft rule in my farthest speculations the animal faith I live by from day to day. [Scepticism and Animal Faith, 1955, p. 308)

This animal faith is guided by biological events, which bring one to beliefs about reason, experience, and art, all of which may be illusory but which lead to various "realms of being" that can be studied, appreciated, and lived in. Another form of twentieth-century skepticism is that of such existentialist thinkers as Albert Camus. Camus built on the fideistic skepticism of Kierkegaard and Leon Shes-tov and the skepticism regarding religion and objective values of Nietzsche. In his Myth of Sisyphus he portrays man as trying to measure the nature and meaning of an essentially absurd universe by means of questionable rational and scientific criteria. Camus regards the skeptical arguments used by Kierkegaard and Shestov as showing the contradictory nature of human rational attempts to understand the world as decisive, but he rejects their fideistic solution: overcoming the skeptical crisis by "a leap into faith." Instead, he accepts Nietzsche’s picture of the ultimate meaninglessness of the world because "God is dead." For Camus, the basic absurdity of the human situation, of man constantly seeking for understanding and meaning in an unintelligible and meaningless world, must be recognized and accepted. In this situation knowledge in the traditional sense is unattainable, and no justifiable, or even plausible, modus vivendi between man’s desires for understanding and worthwhile goals and the absurd conditions of his existence can be found. The mythological Sisyphus, eternally pushing a huge rock uphill, only to have it fall to the bottom again, typifies the human situation. Sisyphus "knows the whole extent of his wretched condition." He does not expect to find truth, nor does he expect to end his struggle. He finds no ultimate point or value in his-situation, but he perseveres with a "silent joy," realizing that his struggle has meaning only for him, in terms of his human condition, and not in any objective frame of reference. The struggle is neither sterile nor futile for him, though it is meaningless in terms of understanding or possible achievement.

This type of skepticism, now quite popular, is allied with a kind of futilitarianism, reflecting the feeling that the optimism of the Enlightenment and the nineteenth century are illusions. The spiritual collapse of hopes for progress, peace, and human happiness in the course of the catastrophes of the twentieth century has led many intellectuals to a fundamental skepticism about man’s capacity to know and understand his world, and about the merits of the ideals he has been striving for. This collapse, coupled with a strong skeptical current running from Bayle, Hume, and Voltaire to Bertrand Russell and others about the value of the religious and moral traditions of the Western world, has turned many philosophers away from any serious quest for genuine knowledge about the nature of reality and has led to the denial of grandiose knowledge claims and any metaphysical or theological system. The turn toward the intensive examination of ordinary belie! and language, and of man’s personal involvement in his allegedly absurd, meaningless situation, is in many ways like the intellectual atmosphere in which skepticism thrived both in Hellenistic times and in the late Renaissance. Well-structured’ worlds had collapsed, and with the collapse of all the frames ol reference no goals any longer seemed obvious or certain. In those periods, as today, the questioning of basic assumptions deepened the disillusionment with traditional Weltanschauungen and led to a quest lor new bases of certainty, knowledge, and values.


Skepticism has been continually attacked and "refuted" in the history of philosophy and has only occasionally been set forth as a serious view. Opponents have argued from Greek times to the present that skepticism is untenable and that it flics in the face of common sense and ordinary beliefs. As Hume admitted, one of the characteristics of skeptical argumentation is that "it admits of no answer, and produces no conviction."

The skeptics from Sextus Empiricus to Montaigne, Bayle, Hume, and Santayana have pointed out that the strength of skepticism lies not in whether it is tenable as a position but in the force of its arguments against the claims of dogmatic philosophers. To avoid leaving his opponents the opportunity to challenge the consistency of skepticism, Sextus carefully avoided stating the view as anything other than a chronicle of his personal feelings at given moments. Montaigne indicated that the Pyrrhonians needed a nonassertive language to state their case, since as soon as they asserted anything, opponents could claim that they had violated their own views. Bayle and Hume pointed out that skepticism, if stated and argued for consistently, would be self-refuting but that this sell-refutation would not take place until skepticism and the opposing dogmatic views had all been undermined.

However, skepticism has not functioned in philosophy as merely one more position alongside idealism, materialism, and realism. Instead, it has been like an anonymous letter received by a dogmatic philosopher who does hold a position. The letter raises fundamental problems for the recipient by questioning whether he had adequate grounds for his assertions and assumptions or whether his system is free from contradictions or absurdities. The recipient may try’ to fend off the attack by challenging whether any philosopher could write the letter without opening himself to similar attacks. By imputing an author, the dogmatist may show the problem involved in consistently stating skepticism, but he does not thereby reply to the arguments in the letter. Skeptical arguments are usually parasitical, in that

•60   Skepticism

they assume the premises of the dogmatist and show problems that ensue, on the standards of reasoning of the dogmatist.

For the dogmatist, the skeptical arguments, regardless of whose they are, pose basic difficulties; and if he sees their relevance to his own views, it is he who must deal with them if he wants to be satisfied that his system is tenable. Sextus set forth his arguments primarily in terms of Stoic and Epicurean views; Montaigne, both in terms of these and of scholastic and Platonic ones; Gassendi, in terms of Carthesian escolastic and Renaissance naturalistic ones; Bayle, in terms of the system current in his day—scholastic, Cartesian, Leibnizian, Lockean; and Hume, mainly in terms of Lockean and Cartesian ones. The upholders of these systems then had the problem of refuting these arguments within their systems, regardless of who in fact posed the problems and whether he believed what he appeared to be saying.

The historical skeptics did not say that they personally regarded everything as doubtful. They distinguished believing various matters from having sufficient reasons for believing them. Regardless of the legends about Pyrrho, the skeptical authors seem to have followed Huet’s view that it is one thing to philosophize and another to live, and that many propositions may be philosophically dubious but acceptable or even indubitable as living options. The problem posed by skeptical probing was not what do, or what must, people believe but, rather, what evidence is there for beliefs, and is this evidence adequate?

From Creek times onward, skepticism has functioned as a gadfly to dogmatic philosophy and as a challenge to keep it honest. The skeptical critique has thrived on the desire to find a coherent and consistent account of our knowledge and beliefs about the world. Had there never been disillusionment about what was accepted as true, skepticism would probably not have arisen. Nevertheless, skepticism has led to continual re-examination of philosophical claims and to new dogmatic systems trying to avoid difficulties in others. This in turn has led to new skeptical attacks and ingenious new criticisms or new versions of criticism. Thus skepticism has been a major dynamic force in intellectual history. And even if many philosophers are now willing to accept Hume’s friend Thomas Blacklock’s observation that "the wise in every age conclude, what I’yrrho taught and Hume renewed, that dogmatists are fools," human foil)’ keeps the quest for knowledge of the ultimate nature of reality going and skeptics keep challenging the latest claims to such knowledge. Without skepticism, we probably could not distinguish enthusiasm, prejudice, or superstition from serious or meaningful beliefs. As Shaftesbury said, after living with Bayle for a while, any views he had that could survive the continuous skeptical onslaught, he regarded as being as valuable as the purest gold. Each age is able to assess the views which are valuable to it only if they are subjected to the same challenge.

(See also Appearance and reality; Certainty; Doubt; Ethical relativism; Fideism; Illusions; induction; irrationausm; nihilism; other minds; Paradigm-case argument; and Solipsism. See Skepti-

cism in Index for articles on individual skeptics and on philosophers especially concerned with rebutting skeptical arguments.)


The following works deal with the history and nature of skepticism. In addition, see bibliographies to articles on specific skeptical thinkers.

Allen, Don Cameron, Doubt’s Boundless Sea: Skepticism and Faith in the Renaissance. Baltimore, 196-1.

Atlas, Samuel. From Critical to Speculative Idealism: The Philosophy of Salomon Maimon. The Hague, 1964.

Bartholniess, Christian, Huet. cheque d’Avranches, ou le scepti-isme theologque. Paris,  1850.

Bcvan, Edwyn, Stoics and Skeptics. New York, 1959.

Boas, Georg, Dominant Themes of Modern Philosophy. New
York, 1957.                                         

Bredvold, Louis 1., The Intellectual Themes of Modern Philosophy. New
Arbor, Mich., 1931.                                            

Brochard, Victor, Les Scepliques grecs. Paris, 1887.

Busson, Henri, Le Rationalisme dans la litterature francaise de la Renaissance. Paris, 1957.

Dambska, Izydora, Sccptycyzm Froncuski XVI i XVII Wicku. Torun, Poland, 1958.

Coedeckemeyer, Albert, Die Geschichte des griechischen Skep-tiziismus. Leipzig, 1905.

Gregory, Tullio, Scetticismo ed empirismo: Studio su Cassendi. Bad, 1961.

Hallie, Philip P., ed., Scepticism, Man, and God. Selections From the Major Writings of Sextus Empiricus. Middletown, Conn., 1964. Edited, with introduction, notes, and bibliography by Philip P. Hallie; translated by Sanford C. Etheridge.

Maccoll, Norman, The Greek Sceptics From Pyrrho to Sextus. London and Cambridge. 1869.

Mcnendez Pelayo, Marcellino. Obras completas. Vol. XLIII, Ensayos de critica filosófica. Santander, 1948. Ch. 2, ‘"De los origenrs del criticismo y del escepticismo y especialmente de los precursores cspaiioles de Kant," pp. 117-216.

Owen, John, Evening With the Skeptics. London, 1881.

Owen, John, The Skeptics of the French Renaissance. London and New York, 1893.

Patrick, Mary Mills, The Gieek Sceptics. New York and London, 1929.

Popkin. Richard H„ "David Hume: His P>rrhonism and His Critique of Pvrrhonism." Philosophical Quarterly, Vol. 1 (1950-19511,385-407.

Popkin, Richard H., "Berkeley and Pyrrhonism." Review of Metaphysics, Vol. 5 (1951-1952). 223-246.

Popkin, Richard H., "David Hume and the Pyrrhnnian Controversy." Review of Metaphysics, Vol. 6 (1952-1953). 65-81.

Popkin. Richard H., ‘The Sceptical Crisis and the Rise of Modern Philosophv." fifties of Metaphysics, Vol. 7 (1953-1954;. 132-151, 307-323, 499-510.

Popkin, Richard H.. "The Skeptical Precursors of David Hume." Philosophy and Phenomenological Research, Vol. 16 (1955J.61-71.

Popkin, Richard H., The History of Scepticism From Erasmus to Descartes. Asscn. Netherlands, I960; New York, 1964. Contains lengthy bibliography on skepticism from 1500 to 1650.

Popkin, Richard H., "Scepticism and the Counter-reformation in France." Archie fur Reformatiomgeschichte, Vol. 51 (1960), 58-88.

Popkin. Richard H.. "Scepticism in the Enlightenment,"’in T. Bcstermann, ed., Studies on Voltaire and the 18th Century, Vol XXVI. Geneva, 1963. Pp. 1321-1345.

Popkin, Richard H., ‘Traditionalism, Modernism and Scepticism of Rene Rapin." Filosofia, Vol. 15 (1964), 751-764.

Popkin, Richard H., ‘The High Road to Pyrrhonism." American Philosophical Quarterly, Vol. 2 (1965). 1-15.

Richter, Raoul, Der Skeptizimus in der Philosophic, 2 vols. Leipzig, 1904-1908. A history’and examination of skepticism from ancient times to the end of the nineteenth century.
Robin, Leon, Pyrrhon et le scepticisme grec. Paris, 1944.

Russcel. Bertrand, Sceptical Essays. New York, 1928.

Saisset, Emile, Le Scepticisme: Aenesidcmc, Pascal, Kant. Paris, 1865.

Sanlayana, George, Scepticism and Animal Faith. New York, 1923; reprinted New York, 1955.

Staudlin, Karl F, Ceschichte und Geist des Skepticismus, 2 vols. Leipzig, 1794.

Tafel, J. F. I., Ceschichte und Kritik des Skepticismus und Irrationalismus. Tubingen, 1834.

Villey, Pierre, Les Sources et l’evolution des essais de Montaigne. Paris, 1908.

Zeller, Eduard, The Stoics, Epicureans, and Sceptics, translated by O. J. Reichel, rev. cd. London, 1880.






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