IN THE SUMMER of 1674, officials of the Dutch court carried out the recommendation of the States of Holland to ban the Theological-Political Treatise, a book that one of its more spiteful antagonists described in an anonymous pamphlet as “forged in hell by the apostate Jew working together with the devil.” It was an inauspicious debut for a work that Steven Nadler calls “one of the most important books of Western thought ever written.”

Poor Spinoza. So noble in intention, so reviled and misunderstood. Born into a Portuguese-Jewish family in Amsterdam during the flourishing years of the newly autonomous Dutch Republic, the brilliant young student “Bento” (or Baruch, as they called him at the synagogue) was only twenty-three years old when, on July 27, 1656, his own congregation on the city’s Houtgracht canal presented him with a formal ban of excommunication for his “abominable heresies” and “monstrous deeds.” The absurdity of this herem, the Hebrew term for the rabbinic ban, is that its recipient had not yet published any of the works that would eventually draw down upon his head violent accusations of atheism and immorality. The Ethics, the genuine masterpiece of speculative metaphysics that would earn him an eternal place in the canon of Western philosophy, did not appear until 1677, when its author was no longer alive. But well before this, rumor had already spread that young Bento doubted the law and denied the existence of God except in the “philosophical” sense, which is to say in the most minimal or heterodox sense that carried a whiff of heresy.

In early January of 1670, the mature philosopher published his most aggressive statement of political and religious criticism, under the compound Latin title Tractatus Theologico-Politicus. Anxious to avoid personal reprisals, he published it anonymously and with a cover page that misstated its place of publication as Hamburg. The measures were prudent, but ineffective. Within about three years its author was exposed and plans were afoot for seizing and suppressing all copies of his book. By the end of the 1670s the Catholic Church, eager not to be outdone, decided that the Treatise deserved a place on the Index of Prohibited Books, together with the Ethics and other opera posthuma, including his correspondence.

Steven Nadler has written a delightfully lucid and philosophically thorough account of the Treatise that helps to explain how and why this singular text became the object of such opprobrium and why we should see its appearance as “the birth of the secular age.” The general thesis is not entirely unique. The last two decades have seen an explosion of literature that celebrates Spinoza as the prophet of modernity. In 1992, Yirmiyahu Yovel authored a two-volume study on Spinoza and Other Heretics, entitled The Marrano of Reason and The Adventures of Immanence, respectively, that explored the question of whether Spinoza deserved the title of “the first secular Jew.” Yovel’s answer was no, but then yes: Spinoza could not have been the first secular Jew because “the concept did not yet exist,” but he was “a lost and suspended Jew, his existential case preceding his explicit ideas and prefiguring forms of Jewish existence in which he could not himself participate.”

Yovel then made this very indeterminacy serve as a paradigm for modern identity. The figure of the Marrano (who suffered persecution after the Spanish reconquista and was forced by circumstance into crypto-religious practice) became for Yovel the model for a species of modern selfhood that first emerged in the seventeenth century. And according to Yovel, Spinoza laid the foundations not only for the modern self, but also for the modern conception of the universe as well. The philosophical identification of God and nature—the thesis of pure immanence—laid down a pattern of naturalistic explanation that would inspire many of the greatest thinkers of modernity, from Goethe to Einstein. In Spinoza’s work, Yovel concluded, we are witnesses to an inaugural event of both history and philosophy that passed “from the world of revealed religion into a world of secular reason and immanence.” In a more recent work, called The Other Within, Yovel deepened and broadened this thesis beyond the case of Spinoza to argue that the Marranos heralded a species of split identity and secularism that now typifies much of modern experience.

Yovel’s wide-ranging and speculative argument in some ways prepared the terrain for the publication in 2002 of Jonathan Israel’s Radical Enlightenment, the first volume of what would turn out to be an astonishingly ambitious work in serial installments on the fortunes of Spinozism in European letters and politics. Successive volumes appeared under the titles, Enlightenment Contested (2009) and Democratic Enlightenment (2011). The guiding thesis of this herculean effort is that Spinoza’s philosophy served as the animating principle for the unfolding of a materialist and radically democratic sensibility that ultimately found its expression not only in works of philosophers and political theorists but also in the most forward looking revolutions of the eighteenth century.

Israel’s indefatigable and uncompromising commitment to his bold thesis has met with admiration and (just as often) with skepticism, especially from historians who suspect that terms such as “materialism” or “radical enlightenment” may be simply too labile and diffuse to serve the explanatory purposes required in a work of this scope. One of the risks of intellectual history on the broad-scale, especially when it involves the study of phenomena as capacious as political ideology, is that the precise contours of a philosophical concept will matter far less than the vague shape it retains as it circulates across time and space. Spinozism, after all, is something far more protean, unconstrained by logic and argument, than Spinoza himself would have liked.

What makes Nadler’s book so welcome a contribution is the care and the clarity of his philosophical exposition, and his restraint when tracing the wider implications of Spinoza’s work. Nadler refrains from bold interpretation—his ambition is the more modest one of faithful reconstruction—and his success on this score is also his book’s greatest virtue. Most of all he aims to remind us why the actual argumentation of the Tractatus Theologico-Politicus warrants its reputation as one of the most revolutionary and exhilarating texts in all of modern philosophy. But he also considers it important that we not lose sight of the biographical and historical questions: Why is it that the Treatise encountered such hostility? Were its claims truly that much more radical than other contemporary works of political theory and religious criticism? And if so, what could have possessed its author to write so scandalous a book?

AFTER HIS EXCOMMUNICATION Spinoza quit Amsterdam, first settling in Rijnsburg, a village near Leiden, where he supported himself as a lens-grinder, and then moving to Voorburg, a hamlet just east of The Hague. He occupied himself with a commentary on Descartes (the sole published work in his lifetime that bore his own name on its cover) and then commenced work on the Ethics, the formidable work of metaphysics that provides the most elaborate statement of his own philosophical vision. It was while he was still busy with a draft of the Ethics that Spinoza felt himself drawn toward more political concerns.

As Nadler explains, local disputes in the Voorburg church pitted conservatives against liberals, and it was somehow suspected that Spinoza was working for the liberal faction. Conservatives spread the rumor that he was an atheist and “someone who mocks all religions,” and thus “a harmful instrument in this republic.” In a letter to Henry Oldenburg, the corresponding secretary for the Royal Society in England, Spinoza complained of “the opinion of me held by the common people, who constantly accuse me of atheism. I am driven to avert this accusation,” he declared, “as far as I can.” It was now his intention to write “a treatise on my views regarding Scripture,” a work that would combat “the prejudices of theologians” and uphold “the freedom to philosophize and to say what we think.”

The Treatise, unlike the Ethics, is, in Nadler’s well chosen words, “a public-minded book.” Its composition was born of personal anguish. Spinoza’s close friend, Adriaan Koerbagh, had been recently tried for blasphemy for writing a book that reputedly denied the divinity of Jesus and the virginity of Mary. Koerbagh was imprisoned and died from the harsh conditions—a portent in Spinoza’s eyes of what could happen to Dutch society at large. The Treatise testifies to the political fears and aspirations of its author at a time when the future of the Dutch Republic still appeared uncertain.

Its great curiosity is signaled already in its title, which conjoins the critique of religion with arguments for a certain form of political order. The question as to how these two orders of discourse can be brought into harmony is nothing less than the “theological-political problem” for which traditional philosophers before Spinoza’s time typically had a readymade answer: the harmony is guaranteed insofar as we recognize God as the transcendent ruler of the world, and, through divine revelation, we have access to the commandments by which we are supposed to order our individual and collective lives. What distinguishes Spinoza’s philosophy most of all from this traditional solution is that he no longer endorses its conception of a radically transcendent and anthropomorphic God. From this follows a new conception of nature and a novel proposal as to how we should understand Scripture, with all of its imaginative tales of miracles and prophecies. All of these new ideas ultimately inform Spinoza’s understanding of what is the best way to lead one’s life and how the political world must be arranged so as to make this life possible.

The revolutionary insight that sets in motion all of the arguments of the Treatise is that “God’s decrees and commandments, and consequently God’s providence, are in truth nothing but Nature’s order.” The identity between divine commands and the system of nature is a metaphysical theme that Spinoza articulated with far greater rigor and detail in the Ethics, the posthumous work which, of course, the first readers of the Treatise could not have known. But it is this theme that lies at the very core of Spinoza’s vision: the universe, he claims, is a single substance, unique, infinite, and absolutely necessary. It is an order without alternative, without contingency or division, and its existence is nothing less than eternal. In the original Latin edition of the Ethics (though not in the more accessible Dutch edition), Spinoza summarizes this explosive idea with the almost casual observation that we may describe this infinite substance as “God or Nature,” or Deus sive Natura.

The Latin term, sive, simply means “or.” Spinoza’s philosophy seizes upon this modest word to announce one of the most immoderate claims in all of modern philosophy. But if it is the pivot for a philosophical revolution, it is all the more crucial that we be clear about which sense of the term its author had in mind. Not surprisingly, it is a term that can be construed in several ways. A man introduces himself with a casual air: “You can call me Benedict or Baruch.” Another person declares her indifference about dinner: “I could have broccoli or Brussels sprouts.” It is fairly clear that Spinoza did not mean indifference (as in the choice of vegetables). It is equally clear that he did mean identity (as in the choice of his own proper name). Yet the idea of mere identity can mislead us as well, since it could imply sheer equivocation about which term is most suitable, as if God were still as good a name as Nature.

But Spinoza did not equivocate. In the history of Spinoza’s philosophical reception, some readers have interpreted this conclusion backwards, celebrating Spinozism as a philosophy that divinizes nature. This interpretation was especially popular amongst the German Romantics, including the philosopher Schelling and, even more famously, Goethe, who declared himself both a Spinozist and a “pantheist.” But as Nadler explains, the divinity-of-nature theme is highly misleading. Spinoza’s Deus sive Natura works more like an elucidation, where it turns out that what the first term really amounts to is the second. When we clarify what the philosophical idea of God really is, it turns out that all of the more anthropomorphic or personalist qualities typically associated with the God of the Biblical tradition must be abandoned.

There were precedents for this in medieval Jewish philosophy, particularly in Maimonides, who claimed that the terms of our mundane language cannot be predicated of a supra-mundane God. But Spinoza went even further. In his cosmos, there is no personal redeemer to whom we might appeal in our distress, and there is no room for a higher creator who dwells outside of nature. Indeed, such a monistic vision allows little room for the traditional conception of God at all. For nature is all that there is; thought and extension are merely its attributes. Nature is infinite and acts with thoroughgoing necessity, but it is utterly indifferent to our individual cares and aspirations. Spinozism, in other words, does not divinize nature, it naturalizes the divine.

One of the more startling consequences of this identification is that it does away with the possibility of miracles. In the Treatise Spinoza explains that because nature is a “fixed and immutable order,” nothing ever happens in nature that does not follow from her laws. But this means that to believe in miracles is already to deny the perfection of the cosmos: if nature required intervention from beyond, this could only because one thought of nature as flawed or in need of occasional adjustment. A perfect divinity does not perform miracles but is identical with the perfection of its creation. To insist on miracles merely betrays one’s failure to grasp the structure of reality: “miracles and ignorance are the same.” A truly virtuous and rational person will recognize his own place in the perfect order of nature and will regard any apparent imperfection with stoic equanimity.

Spinoza’s conception of nature may have banished miracles, but it thereby contributed in a positive way to our modern faith that the physical world is a realm of lawful regularities. It is an important premise of natural scientific reasoning that we expect the order which obtains in one precinct of physical space to obtain in another precinct as well. Boyle’s experiments with vacuum pumps would have been inconsequential were it not for the underlying premise that events demonstrable in the laboratory could be in principle reproduced wherever physical law held sway (which is to say, everywhere). This remains a crucial premise for Newtonian physics: the very law of universal gravitation would not otherwise count as a law. Historians of early-modern science have argued that this metaphysical principle amounts to a kind of “secular theology.” The assumption that the natural order is perfect and its laws necessarily inviolable across all possible variations of space and time does not actually surrender but instead secularizes the idea of divine perfection. Einstein’s well-known passion for Spinoza and his rejection of probabilistic reasoning in quantum physics stems from this premise: that God (that is, Nature) “does not play dice.” Spinoza was in this sense a paradigmatic philosopher of the scientific revolution: he provided a metaphysical warrant for our trust in nature’s perfection.

In the Treatise, Spinoza brings this naturalistic understanding to bear on the Bible. In his view, Scripture is a thoroughly human document, and if we scrutinize it in a scientific fashion, with sufficient attention to its full welter of historical and linguistic detail, we will be compelled finally to recognize its imperfection and (therefore) its non-divine origin. The Bible, Spinoza argued, is “faulty, mutilated, adulterated, and inconsistent.” Much of the Treatise consists of a deliberate and merciless dismantling of its miraculous reports and, most of all, its moral codes. For the entirety of this “mutilated” text, in Spinoza’s view, contains little more than one lesson that is truly of value: “Love your neighbor as yourself” (Leviticus, 19:18) and “He who loves his neighbor has satisfied every claim of the law.” (Romans 13:8). But the final blow to the authority of the text is that even this lesson can be learned in other ways. “He who is totally unacquainted with the Biblical narratives,” Spinoza writes, “but nevertheless holds salutary beliefs and pursues the true way of life, is absolutely blessed.”

From these arguments it followed that prophecy did not involve some kind of privileged insight into a higher sphere of reality. A Biblical prophet is merely a human being who possesses an especially vivid imagination and conveys knowledge and moral insight in concrete images rather than in a purely intellectual form as does the philosopher. Spinoza further derived from his naturalistic principles that no historical religion deserved the prestige of a unique claim to revealed truth. The laws of Judaism were merely the laws of a particular well-ordered polity and with the collapse of ancient Israel Judaism itself had lost its validity. The dogma of election had no other meaning: “The Hebrew nation was chosen by God before all others not by reason of its understanding nor of its spiritual qualities, but by reason of its social organization and the good fortune whereby it achieved supremacy and retained it for so many years.”

THE NATURALISTIC AND this-worldly conception of religion set forth in the Treatise already sufficed to warrant its reputation as a “book forged in hell.” But the ideas that marked it as truly revolutionary (or scandalous) were political: the best form of government, according to Spinoza, is one that permits the individual to exercise his own rational will. Obedience to laws simply because they are imposed is analogous to the irrational condition that Spinoza described in the Ethics as enslavement to the passions. In both cases one is merely responsive to external commands. Both monarchy and aristocracy therefore represent “an infringement of freedom” whereas democracy by contrast most closely approximately “that freedom which nature grants to every man.”

Was Spinoza a liberal in the modern sense? Nadler warns us against such language chiefly because it may obscure what is most distinctive in the political doctrines of the Treatise. Since the teachings of religion, for Spinoza, retained their validity only insofar as they promoted moral conduct and public order, he saw nothing offensive in the idea that the sovereign should control religious laws as well. For a democracy this means that it would be left to the governing bodies to determine the character of God’s law. Such a proposal is a bit shocking to modern readers, but as Nadler explains it clearly reflects Spinoza’s own apprehension that the orthodox Calvinists were threatening the secular authorities. The doctrine nonetheless belongs more properly to the tradition of civic republicanism than to classical liberalism, since it aims to shape the individual for the sake of his own flourishing as a citizen.

The collapse of religion into a civic religion fully directed by the state makes it difficult to characterize Spinoza as a liberal without risk of anachronism. But Spinoza was nevertheless, in Nadler’s view, “one of history’s most eloquent proponents of secular, democratic society and the strongest advocate for freedom and toleration in the early modern period.” Still, Spinoza may have been less concerned with freedom for the sake of politics than for the sake of philosophy itself. The highest ideal of the Treatise is libertas philosophandi, the freedom to philosophize. Although civil religion is designed to fashion better citizens, a government “that attempts to control men’s minds is regarded as tyrannical, and a sovereign is thought to wrong his subjects and infringe their right when he seeks to prescribe for every man what he should accept as true and reject as false, and what are the beliefs that will inspire him with devotion to God.” Sovereignty reaches its limit when it runs up against our capacity to determine for ourselves and on the basis of our own reason what we consider right and wrong. These are, in the words of the Treatise, “matters belonging to individual right, which no man can surrender even if he should so wish.”

Spinoza did not trust his contemporaries to embrace such arguments, and he probably would have feared for his own life if they were to be promulgated too freely and in a climate prone to misunderstanding and retribution. Even before the Dutch court enacted its official condemnation of the Treatise in 1674, Spinoza decided it would be best to refrain from issuing a translation in Dutch. Although this would have made the text immediately accessible to a far wider audience in the Netherlands, its author was simply naïve if he believed his arguments could remain secret for very long. Spinoza died, at the age of forty-four, in 1677, and a clandestine French translation was issued the next year. From there it began its travels across all of Europe and would serve as a major inspiration for critics of religion and advocates for democracy well into the eighteenth century.

Tracing the book’s reception (as Jonathan Israel has done) remains a terrific challenge, because so many of its themes lost in precision what they gained in influence—the typical fate for philosophical concepts when they are released into the world. The problem proves especially difficult when one attempts to determine the worldly impact of metaphysical ideas rather than political ones. For Nadler as for Israel, the story of the Treatise is nothing less than the story of modernity’s unfolding. But metaphysics and politics do not always align so neatly. The particular metaphysical doctrine that was born with Spinoza—a stringently rationalistic species of monistic naturalism—does not dovetail in any obvious way with our experience of ourselves as moral agents. For Spinoza, freedom and monism may have seemed compatible. For a great many other philosophers, however, they stand in starkest conflict. Kant, for example, should be credited as much as Spinoza for working out the principles that underwrite our modern notion of freedom—but Kant recoiled from naturalistic monism, and cleaved instead to the idea of freedom as a “miracle in the phenomenal world.” Not all miracles, it seems, vanished with the death of God.

The obvious lesson to be taken from this example is that “Spinozism” can mean a great many things. It is not a unified package that has survived intact across the centuries. Such questions notwithstanding, the expressly political ideas we owe to Spinoza are still very much with us even today. And in this respect we are indeed, as Nadler observes, “the heirs of Spinoza’s scandalous treatise.

Peter E. Gordon is the Amabel B. James Professor of History at Harvard. He is the recipient of the Jacques Barzun Prize from the American Philosophical Society for his most recent book, Continental Divide: Heidegger, Cassirer, Davos.