Tuesday, 30 March 2010

Metaphysics I

This is the first part of an introduction to some of the metaphysical themes that you may find useful for reading St. Thomas. For more information on these topics, have a look at some of the books suggested here.

Metaphysics I

This little document is intended to be the first part of a short introduction to the metaphysical themes that St. Thomas takes for granted in the summa theologiae. Here we shall cover the material appropriate to the first part of summa, up to but not including his treatment of the Trinity. It cannot pretend to be anything other than highly selective and the reader should be aware that it glosses over most of the arguments contained in it. For a more comprehensive and in depth treatment of the themes covered here, the reader is referred to the books suggested on the website. In particular, Feser’s “Aquinas: A Beginner’s Guide” and his “Scholastic Metaphysics”.

In The Beginning
In the very early days of civilization, at the birth of what we now know of as “philosophy”, many of the concepts that we take for granted were eagerly debated among the philosophers. One of those early questions concerns being itself. When we observe the world around us, we notice that some things come into existence and some things go out of existence. Also, some things change their form but remain identifiably the same “thing”. For example, an individual human being is born, grows and eventually dies and decomposes. While they are growing they remain the same individual but the matter they are made out of is constantly changing. Two big questions arise: “how is it that things can change whilst remaining the same thing?” and “What is it that exists when we say that a thing exists?” The second question may look rather odd, but consider this: if an object exists then it seems redundant to say that the object itself exists. But if the object does not exist, there is no object about which we can say that it does not exist.

Two early philosophers who considered these sorts of questions were Heraclitus and Parmenides; they came up with diametrically opposed ideas about being. Heraclitus considered the persistence of things through change and came up with the idea that there is no such thing as “being”, but only “coming to be”. The saying that “you never step in the same river twice” is associated with him. Parmenides, on the other hand, argued that a being could change only if caused to do so by something other than it. But firstly, the only thing other than being is non-being and non-being, since it is nothing, cannot cause anything and secondly being cannot cause itself. Therefore there cannot be change.

These arguments (especially that of Parmenides) may look strange to us today (and what I’ve described above is very much simplified and filtered through the eyes of their critics), but it is important to remember that we have absorbed over two millennia’s worth of thinking about being – Heraclitus and Parmenides were in at the start of this thinking.

Two great thinkers of the ancient Greek world were Plato and Aristotle. It’s from them, considering these great questions about being, that we inherit the vocabulary of ideas with which we consider these questions today.

Forms & Universals

Plato’s big idea was that of “forms”: a form captures the “essence” or “nature” of a thing; what makes it what it is and distinguishes it from anything else. For example, we are all aware of instances of triangles, and we are all aware that they are, to a better or to a worse degree, an approximation to what we might think of as an “ideal” triangle. This notion of an ideal triangle is the “form” of a triangle.  All actual triangles instantiate, to a better or worse degree, the form of a triangle.

It’s not unreasonable to suppose that when we know the essence of triangularity in this way, we know something “universal” rather than something just particular. But Plato wanted to say more than just this. He thought that such essences or forms are known to the intellect by abstraction from concrete things, but that they are not merely mental objects. These forms live in a sort of “third realm” beyond concrete particulars and beyond the intellect. However, these forms don’t live “somewhere”; the existence of their “third realm” proves that reality is richer than just “where”. He thought that the world of material things is a faint copy of the realm of the forms.

Therefore, particular things (imperfectly) participate in or exemplify or instantiate their form. Material things come and go; forms are eternal (outside time & space) and unchanging. In fact, Plato considered that forms are more real than the things that instantiate them.

It’s worth noting some of the consequences of Plato’s theory of forms. Such a theory points towards a notion of goodness. For example, something can be a better triangle than another by participating more perfectly in the form of triangularity. But more than this, one can construct a theory of morality; if we participate in our forms, then our goodness can be measured by the degree to which we participate in our forms. A “good” human is one who is “most” human. And beyond this, Plato gives a special emphasis in his writing to the “form of the Good”. Plato may have seen this as being God (it’s not entirely clear in his writings); the neo-Platonists certainly did.

We’ve mentioned above that forms are in some sense “universal” objects in that they give an ideal form to particular concrete objects. Indeed, forms are considered to be examples of the wider class of “universals”. Numbers and propositions give examples of universals that are not considered to be forms. The idea that universals have a real existence is called “realism”. As we’ve indicated, Plato held to a particularly strong version of realism, where universals have an unchanging existence in a realm of their own. In contrast, the idea that universals exist only in the mind is called “conceptualism”; that they do not exist at all is called “nominalism”.

It’s worth noting that in his theory of forms, Plato compromises with Parmenides. Although concrete objects can undergo change, the forms themselves are eternal and unchanging. Plato has kicked Parmenides’ unchanging world upstairs!

The form of realism that Plato held is not the only possible form of realism. For Aristotle and for Aquinas, much later on, forms are still “real” but they only exist “in” the things they are the forms of. This form of realism is sometimes called “moderate realism”. We’ll see more about this below.

Actuality & Potentiality (Act & Potency)

Aristotle was also motivated by the wish to refute Parmenides, but he did not agree with Plato’s solution. Aristotle argues that Parmenides’ central argument is false because being and non-being are not the only two alternatives for the source of being (and he notes that Parmenides’ argument depends upon equivocation over the meaning of “being”). He points out that existing things don’t just exist; they also have potential to exist in different ways. So he argues that existing things have both their “actuality” (which denotes how they actually are now) and their “potentiality” (what they might become in future). Furthermore, a thing’s potentiality is rooted in its nature, what it actually is. A particular concrete object doesn’t have the potential to be just anything at all. Actuality and potentiality are defined in relation to one another, but actuality has metaphysical priority over potentiality. For example, any potentiality is a potentiality for some actuality. Actuality can exist on its own (e.g. in God) but potentiality cannot.

A hugely important principle is that no potentiality can actualize itself. For potentiality to become actuality, a “cause” has to be involved. Whatever is changed is changed by another; or in traditional language, whatever is moved is moved by another.

Actuality and potentiality exist in a sort of hierarchy. For example, a human being such as you is a rational animal and therefore has the power of speech; and because you have this power, you can sometimes exercise this power. You actually having the power of speech flows from you being a rational animal, it is a “secondary actuality” to the actuality of being rational. Similarly, actually speaking is a secondary actuality to having the power of speech. Similarly with potentiality: if you do not know the German language, you still have the potential to learn it as you are a rational animal. You have a “first potentiality” for speaking German. If you do learn it, you won’t be speaking it all the time, but you now have the “second potentiality” for speaking it at any given moment. Also note the linkage between potentiality and actuality: in knowing how to speak German you now have a new primary actuality and actually speaking it is a secondary actuality relative to this.

So, in suggesting that all things are a mixture of actuality and potentiality, and by suggesting that causes are responsible for actualizing potentiality, Aristotle has built a metaphysical system that allows for and explains change. We now need to see how he explains the persistent identity of things through change.

(N.B. For reading Aquinas and his commentators, it is important to note that actuality and potentiality are often called “act” and “potency”.)

Form and Matter

Heraclitus argued that only change exists. Human beings change the stuff that they are made of many times throughout their lives; therefore it makes no sense to consider them as beings but only as “coming to be-ings”. We’ve seen how Plato’s theory of forms attempts to address how identity persists through change. We now look at how Aristotle modified Plato’s theory and incorporated it into his own.

Aristotle has already observed that the ordinary objects of our experience are irreducible (i.e. inseparable) composites of potentiality and actuality. They have the capacity to change but they also persist in their identity through that change. Aristotle’s approach to the latter feature of reality is his theory of “hylomorphism”. The ordinary objects of our experience are composites of “matter” and “form”.

If we consider an everyday object, the things that are essential to it being what it is (i.e. its essence) comprise its “substantial form”; the things that are inessential correspond to its “accidental forms”. For example, being a rational animal is the substantial form of human being; being black or white skinned is accidental to being a human being.

Forms themselves form a hierarchy: at the top level is the substantial form that makes a thing what it is; next there are things, called proper accidents that necessarily flow from the substantial form; and finally, there are accidental forms. As an example of a proper accident, risibility follows on from being a human being. One might also consider matter in a hierarchy: a rubber ball is made out of rubber; a block of rubber is made out of atoms of rubber; atoms of rubber are made out of quarks and gluons and so on. The series terminates in what is called “prime matter”; something that never exists on its own but is always “informed” to produce an object. Prime matter is a basic building block of Aristotle’s theory; the closest analogue in modern science is probably energy.

Form and matter are inseparable. If we consider a rubber ball, what exists in our world is the ball itself. Neither the form of the ball nor the matter of the ball exists by itself. (If the rubber were not in the form of a ball, it would have to be in the form of something else, a block of rubber for instance.) They are still real, though! They are aspects of reality different to those that we normally consider. The form “exists” insofar as the rubber has taken on the form of a ball. One should think of form and matter as being co-principles of actual beings.

In Aristotle’s theory it is sometimes said that form is what “determines” matter and matter is defined in terms of its potential to take on different forms. Form “limits” matter to be particular objects. We must also note that matter is what “individuates” things; a form is a potential for many different individuals, but once a form informs some matter, we have an individual thing.

So in summary, actuality and potentiality allow for change to exist; matter and form allow for things to persist through change. We shall soon see that cause binds these pairs together to allow persisting things to change. Thus Aristotle refutes the theories of Parmenides and Heraclitus together.

We must also note that actuality and potentiality are more general than form and matter; for example, immaterial objects such as angels can exist. Also, form is metaphysically prior to matter; pure immaterial forms can exist; for example, the human soul.

It’s worth pointing out that elementary treatments of form and matter often use examples that are artifacts; that is, things that constructed by some intelligence. So a lump of bronze is said to be given the form of a statue by the sculptor; similarly, our rubber ball above is an artifact. These simple examples give the impression that the notion of form can simply be reduced to the idea of certain configurations, structures or shapes. Notice however, that the shape of a bronze statue is an accidental form imposed upon the lump of bronze by the sculptor rather than its substantial form. Distinguishing the accidental from the substantial; and understanding what substantial form consist in can sometimes be difficult. See the references for a further treatment.

The Four Causes

Aristotle must now bind the theories of actuality and potentiality together with those of form and matter. He does so with his notion of “causes”. To specify the causes of something is to give a full explanation of it. Causes provide answers to questions like: What is it made of? What characterizes it? Where did it come from? How did it come to be? What is it for? In Aristotle’s theory there are four fundamental causes:

  • Material Cause: the stuff that something is made from.
  • Formal Cause: What is the form, structure or pattern of the material in the thing that makes it what it is? So the material and formal causes are just a thing’s matter and form considered as explanations of it. Basically, a thing’s formal cause is its substantial form.
  • Efficient Cause: That which brings the thing into being in the way that it is. That is, that which actualizes its potentiality.
  • Final Cause: the end, goal or purpose of a thing.

It’s tempting to identify efficient causes with our modern notions of causation in the materialistic sense. There is a similarity but it is a similarity that can mislead. In the Aristotelian scheme, efficient and final causes go together (in a fashion similar to formal and material causes going together). One doesn’t really make sense without the other.

The modern tendency is to treat cause and effect as a relationship between temporally ordered events. Such events are seen as not necessarily connected but connected by constant conjunction (this is Hume’s approach) and thus we infer causal “laws” by induction. Aristotle simply would not have recognised this. To Aristotle, things are causes, not events. He would argue that the immediate efficient cause of an event is simultaneous with the event, not temporally prior to it. So if I were to throw a brick through a window, Hume would argue that the previous constant conjunction of the events “a brick is thrown at a window” and “the window shatter” would justify us in saying that the first event caused the second. Aristotle would argue that the brick in contacting the window causes the window to break; it is in the very nature of this kind of contact that the brick breaks the window and is the cause of the window breaking. Aristotle’s model of causation might also be illustrated by thinking of a potter forming a clay pot on the wheel; there is intimate contact between cause and effect.

The analysis of any event resolves into a series of causes intimately related in this way. Such immediate efficient causes imply a series of simultaneous causes and effects. Thinking this way leads us to the notion of a “per se” (or “substantial”) series of causes. Aquinas exploits this structure in the “five ways”. For example: a stick is pushing a stone; the stick is pushed by the hand; the hand is pushed by arm muscles; the arm muscles are activated by neurons firing in the brain; and so forth. Aquinas (and Aristotle before him) argues that this type of sequence must terminate at a first uncaused cause and that this cause is what we call God. One contrasts a per se series of causes with a “per accidens” (or “accidental”) series of causes. A man has a son, who himself has a son. One may quite rightly identify this as a series of causes, but there is no need for the first cause of the series to still exist at the time of the second cause (he may have since died, for example). Aquinas is quite happy to concede that such a series might be infinite, with no first cause.

A fundamental principle of causation described in this way is that the effect must in some way be related to what is in the cause. This is sometimes expressed by saying that effects resemble their causes or that a cause cannot give to its effect what it doesn’t have to give. We use this principle every time we try to solve a causal conundrum: “what could possibly have caused this?” We will always look for possible explanations that are consistent with the effect itself. If we find a broken window, we will start thinking in terms of something hitting the window or of some manufacturing stress in the window; we won’t start looking for a leaking pipe.

Effects can be “contained in” their causes in various ways. If the cause has the feature that it generates in the effect, it generates the effect “formally”. If it doesn’t have the feature but has the inherent power to produce the feature, then is generates the effect “eminently”. A blazing fire causes the stick thrust into it to catch light formally, but a match causes fire eminently when it is rubbed against the match box.

The final cause of something gives an indication of the thing pointing to an end beyond itself. Inherent within the acorn is oak tree into which it will grow. In Aristotle’s (and Aquinas’) world everything is in some sense directed towards some goal; things exhibit purpose. For example, divine revelation tells us that the end of human being lies in the beatific vision. In terms of actuality and potentiality, final causes direct efficient causes to actualize the potential in things. They may only frustrated in that actualization by other things being actualized in their own potentials. For example, the growing gazelle ordered towards its adult form would be frustrated by being eaten by a lion doing the same thing.

According to Aquinas, a final cause is the “cause of all causes”. Material causes underlie the potential for change; potentialities are potentialities-for, directed towards some actuality. Therefore final causes underlie all potentiality and thus materiality.  Final cause also determines formal cause; it’s only because a thing has a certain end or purpose that it has the form it has. Similarly, efficient causes are directed towards actualising a potentiality by final causes.

Essence and Existence

According to Aquinas there is a distinction between what a thing is and that it is; between its “essence” and its “existence”. This is related to Aristotle’s distinction between act and potency. Remember that the form of a thing actualizes its potentiality; it makes a thing the sort of thing that it is. But there’s nothing about a form (and thus an essence) that guarantees that it exists or informs anything. Her Majesty the Queen, Socrates and Batman, being human beings, are composites of form and matter. However, the latter two do not exist, being dead and fictional respectively. So, though actual relative to matter, a form or essence is only potential with regard to existence or being. Existence is what actualizes a form or essence.

Genus and Species

A “genus” is a general kind of thing which encompasses a number of “species”, each of which are differentiated one from another in terms of their “differentia”. For example: humans, dogs and snakes are all species of the genus animal; humans can be differentiated from the other two by their being rational (among other things).

The Categories

The idea of the “categories” is to enumerate everything that can be expressed about an object that we can observe, in the most non-redundant way possible. This then implies that the categories enumerate anything that can be the subject or the predicate of a proposition. In Aristotle’s analysis, there are ten categories:

  • Substance” (or “essence”): This describes particular things (for example: Socrates) or universals (for example: man). Sometimes the former are called “primary substances” and the latter “secondary substances”.
  • Quantity”: How much there is of something, the extension of an object. (For example: two feet long.)
  • Quality”: That which characterizes the nature of an object. (For example: white, rough.)
  • Relation”: How an object may be related to other objects. (For example: double, half.)
  • Place”: The position of an object in relation to its environment. (For example: in the marketplace.)
  • Time”: The position of an object in the course of events. (For example: yesterday.)
  • Position”: The end point or position of an object after an action. Also, the relative positions of the parts of an object given a state of rest. (For example: lying, sitting.)
  • State”: The condition of rest after the reception of an affection (see below). Also the things associated with an object. (For example: has shoes on.)
  • Action”: The production of change in some other object. (For example: cutting burning.)
  • Affection”: The reception of change from some other object. (For example: being cut, being burnt.)

The Transcendentals & Analogy

In general terms, the “transcendentals” are properties of being that transcend any of the ten categories. If we think about being itself, then the things we’ve been looking at like act & potency, form & matter, essence & existence, substance & accident, are all aspects of being. But they don’t define being, and we cannot define being in the same way that we might define a species like humanity by specifying a genus of animal and the differentia that specify what it is to be human. Similarly, being can’t be considered to be a genus because we can’t specify species within this genus because we can’t add anything to the notion of being that identifies such species.

However, we need to be able to differentiate the concept of being because it is not an “equivocal” concept (that is, pointing to things that mean completely different things), nor is it “univocal” (that is, pointing uniquely to one sort of thing) as we can apply the term in different ways to different things that exhibit being in different ways. For example, accidents and substance both have being but accidence cannot exist independently of substance; material things are composites of form and matter whereas angels are forms without matter. Created things and God both have being but in created things essence and existence are separate. In each case, the being of one is “analogous” to the being of the other; it is neither completely identical nor absolutely incomparable.

Being is one of the transcendentals. In the Thomist system, there are other transcendentals, namely: “thing”, “one”, “something”, “true” and “good”. Moreover Aquinas argues that each of these is “convertible” with being in the sense that each designates one and the same thing under a different aspect. (The transcendentals differ in “sense” but not in “reference”, to put it in modern terminology.) For example, a thing is just a being of one kind or another; something is either a being among other beings or being as opposed to non-being. To see that the others are convertible is harder and Aquinas spends quite some time arguing such in the early part of the summa. Also see the very opening of his “Disputed Questions on Truth” where he argues that truth and being are convertible.


Followers of Thomas Aquinas have, throughout the ages, attempted to abstract fundamental principles from his work. In the case of the metaphysics that he takes for granted, you may come across the following ideas.

  • The Principle of Contradiction”: “One and the same thing, remaining such, cannot simultaneously both be and not be.”
  • The Principle of Identity”: “If a thing is, it is; if it is not, it is not”. (“being is not non-being”)
  • The Principle of Sufficient Reason”: “Everything that is has its raison d’être (i) in itself, if of itself it exists or (ii) in something else, if of itself it does not exists.”
  • The Principle of Substance”: “That which exists as the subject of existence is substance, and is distinct from its accidents or modes.”
  • The Principle of Efficient Causality”: “Every phenomenon presupposes an antecedent phenomenon.”
  • The Principle of Finality”: “Every agent acts for a purpose.”
  • The First Principle of Practical Reason”: “Do good, avoid evil.”

Another important series of principles goes under the title “the Twenty Four Theses”. These were abstracted from the writings of St. Thomas by the Sacred Congregation for Studies in the wake of Pope St. Pius X’s efforts to combat modernism. I’ve linked to these in the sidebar of the blog. I don’t want to explain them here, but I do have in mind a project to explain them on my blog “From the Desert”; so keep an eye out!

Saturday, 13 March 2010

More Books on Aquinas

If you’ve read some (or all!) of the introductory books on Aquinas, then you’ll probably already have some ideas about what you want to look at next. At this point the literature on Aquinas explodes with possibilities! You should feel free to set off in whichever direction you feel like, but I thought I’d make a few suggestions based on the directions I’ve wandered around in the past few years.

The following are excellent books, at an intermediate level, surveying Aquinas’s work. The first is theologically inclined, the second focuses more on the philosophical aspects of Aquinas.

Rik van Nieuwenhowe, Joseph Wawrykow (eds.), “The Theology of Thomas Aquinas”, University of Notre Dame Press.
Norman Kretzmann, Eleanore Stump, “The Cambridge Companion to Aquinas”, Cambridge University Press.

The following is now regarded as the “standard” biography of Aquinas. The second volume focuses on the spirituality of St Thomas; I think this latter a very important volume as it’s easy to lose sight of the spiritual when the common doctor leaves us gasping for breath with the power of his rationality. The problem is this: if you have lost sight of St. Thomas’s spirituality, you may very well have lost the plot entirely!

Jean-Pierre Torrell, “Saint Thomas Aquinas” (Volume 1, “The Person & His Work”, Volume 2, “Spiritual Master”), Catholic University of America Press.

The next suggestion may be easier to handle if you have some background knowledge of the Anglo-America tradition of analytic philosophy. A superb but lengthy book.

Eleanore Stump, “Aquinas”, Routledge.

These next two are companion volumes of collected essays. In general the quality of the essays is very good (some are quite advanced). The first looks at Aquinas’s work from the point of view of Christian doctrine, the second focuses on his scriptural commentaries (of which there are many).

Thomas Weinandy, Daniel Keating, John Yocum (eds.), “Aquinas on Doctrine”, T&T Clark.
Thomas Weinandy, Daniel Keating, John Yocum (eds.), “Aquinas on Scripture”, T&T Clark.

Questions 27-43 of the first part of the summa are devoted to God as Trinity. For a detailed consideration of these questions in the context of Aquinas’s teaching on the Trinity outside of the summa, and in the context of the teaching of other medieval theologians, perhaps the best easily available treatment is

Gilles Emery, “The Trinitarian Theology of St Thomas Aquinas”, Oxford University Press.

The second part of the summa concerns moral theology. When we eventually get to it you may wish to have a look at the following collection of essays which, between them, provide a thorough commentary on the second part. In general the essays are of very good quality with only a couple which disappoint.

Stephen Pope, “The Ethics of Aquinas”, Georgetown University Press.

The next one is a classic. I’ve never found McInerny’s books easy to read, but they’re worth the effort. This one is a brief summary of Aquinas’s ethical thought.

Ralph McInerny, “Ethica Thomistica”, Catholic University of America Press.

If you want a look at St. Thomas’s thought within the context of Catholic moral teaching then Cessario’s two books are an excellent introduction.

Romanus Cessario, “Introduction to Moral Theology”, Catholic University of America Press.
Romanus Cessario, “The Moral Virtues and Theological Ethics”, Notre Dame University Press.

Servais Pinckaers has been an important figure in the resurgence of Catholic Moral thought (especially after the encyclical “Veritatis Splendor”). He also played a key role in the writing of part 3 of the Catechism of the Catholic Church. What is attractive about his writing is the close synthesis of Thomistic moral thought with scriptural teaching. The first book is a summary and introduction to the much more substantial second.

Servais Pinckaers, “Morality: The Catholic View”, St. Augustine’s Press.
Servais Pinckaers, “The Sources of Christian Ethics”, Catholic University of America Press.

Anything Fergus Kerr writes is worth reading. This is one of my favourites.

Fergus Kerr, “After Aquinas: Versions of Thomism”, Blackwell.

Thomistic thought didn’t stop with St Thomas. Being such an attractive system, commentators and theologians developed the ideas further throughout the centuries. Cessario’s book is very short introduction to that story. It’s a straightforward read and very interesting but really makes one wish that someone would write “A Long History of Thomism”!

Romanus Cessario, “A Short History of Thomism”, Catholic University of America Press.

St Thomas wrote much more than just the summa (which you can see if you follow the links in the sidebar) and there’s still a fair amount of his oeuvre not yet translated into English. If you want a flavour of his other work, a collection of excerpts is the place to start. There are many editions of selections from his writing, but the following are good, cheap and easy to obtain.

Ralph McInerny, “Thomas Aquinas; Selected Writings”, Penguin.
Timothy McDermott, “Thomas Aquinas: Selected Philosophical Writings”, Oxford University Press.

Books on Metaphysics

To understand St. Thomas better, it helps to have some background knowledge of the metaphysical structure of thought he inherited and developed. As a starter, I suggest:

Edward Feser, The Last Superstition, St. Augustine’s Press.

I’ve mentioned this book before as a robust refutation of the so-called “New Atheism”. It’s also a very good introduction to the whole stream of Aristo-Thomist thought through the centuries.

Once past this introduction, this forthcoming book from Feser is likely to become the primary recommendation.

Edward Feser, Scholastic Metaphysics, Editiones Scholasticae. (ISBN 978-3-86838-544-1).

The following three books give excellent presentations of the range of Aristotle’s philosophy.

Christopher Shields, Aristotle, Routledge.
Jonathan Lear, Aristotle, the Desire to Understand,  Cambridge University Press.
Jonathan Barnes (ed.), The Cambridge Companion to Aristotle, Cambridge University Press.

Although neglected in modern times, Aristotle’s thought is not dead! If you want to see a thoroughly modern presentation of where Aristotelianism is today, try the following:

David Oderberg, Real Essentialism, Routledge.

It's well worth looking out some of the older treatments of Aquinas's philosophical system. Some have to be found second hand or on Google Books, but an increasing number of re-prints are becoming available.  Examples of this type of literature are:

A.D. Sertillanges, Foundations of Thomistic Philosophy, in the Catholic Library of Religious Knowledge series published by Sands & Co./Herder Co.
R.P. Phillips, Modern Thomistic Philosophy, Vol 1. The Philosophy of Nature and Vol. 2 Metaphysics, Burns, Oates & Washbourne ltd.
Henri Renard, The Philosophy of Being, Kessinger.

More general than these, the first is a gentle introduction, the second a compact sophisticated survey of everything, very useful as a reference.

Daniel J. Sullivan, An Introduction to Philosophy, Tan Books.
William A. Wallace, The Elements of Philosophy, St. Pauls.

The so-called “Neo-Scholastic” movement of the late nineteenth into the middle of the twentieth century faded into obscurity after the second Vatican Council as the flights of fashion favoured other approaches to the metaphysical foundations of theology. As the weaknesses of such foundational approaches have been more clearly understood, the “classical” Aristo-Thomism of the neo-scholastic movement is regaining the attention it deserves. One figure in particular seems to be gaining favour: Reginald Garrigou-Lagrange. Here are two books of his: the first is a thorough-going summary of neo-scholastic Aristo-Thomistic metaphysics (and more); the second an extended exposition of natural theology (so making up a commentary on the first few questions of the summa). These are not easy going!

Reginald Garrigou-Lagrange, Reality: A Synthesis of Thomistic Thought, Ex Fontibus.
Reginald Garrigou-Lagrange, God: His Existence and His Nature (2 volumes), Ex Fontibus.

I haven’t covered Plato or neo-Platonism or the stream of thought that comes from Augustine in this post. That will have to follow!