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F G H I J K L M N O P Q R S T U V W X Y Z
Metaphysics is taken by Thomas Aquinas to be the study of being qua being, that is, a study of the most fundamental aspects of being that constitute a being and without which it could not be. Aquinas’s metaphysical thought follows a modified but general Aristotelian view. Primarily, for Aquinas, a thing cannot be unless it possesses an act of being, and the thing that possesses an act of being is thereby rendered an essence/existence composite. If an essence has an act of being, the act of being is limited by that essence whose act it is. The essence in itself is the definition of a thing; and the paradigm instances of essence/existence composites are material substances (though not all substances are material for Aquinas; for example, God is not). A material substance (say, a cat or a tree) is a composite of matter and form, and it is this composite of matter and form that is primarily said to exist. In other words, the matter/form composite is predicated neither of, nor in, anything else and is the primary referent of being; all other things are said of it. The details of this very rich metaphysical landscape are described below.
Table of Contents
The Nature of Metaphysics
Essence and Existence
Substance and Accident
Matter and Form
References and Further Reading
1. The Nature of Metaphysics
Saint Thomas, that is, Aquinas, clarifies the nature of metaphysics through ascertaining its particular subject-matter, its field of investigation. In order to ascertain the subject-matter of any particular science, Thomas distinguishes between the different intellectual operations that we use when engaged in some particular scientific endeavor. Broadly speaking, these fall into two categories: the speculative and the practical. Concerning some sciences, the intellect is merely speculative by contemplating the truth of some particular subject-matter; while concerning other sciences, the intellect is practical, by ascertaining the truth and seeking to apply. There are thus correspondingly two distinct classes of science: speculative science and practical science. Speculative sciences are those that contemplate truth whereas practical sciences are those that apply truth for some practical purpose. The sciences are then further distinguished through differentiating their various subject-matters.
Insofar as the speculative sciences merely contemplate truth but do not apply it for some practical purpose, the subject-matter of the speculative sciences is that which can be understood to some extent. Working within the Aristotelian tradition, Thomas holds that something is understood when it is separated from matter and is necessary to thing in some respect. For instance, when we understand the nature of a tree, what we understand is not primarily the matter that goes to constitute the tree in question, but what it is to be a tree, or the structuring principle of the matter that so organizes it and specifies it as a tree rather than a plant. Furthermore, assuming our understanding is correct, when we understand a thing to be a tree, we do not understand it to be a dog, or a horse, or a cat. Thus, in our understanding of a tree, we understand that which is necessary for the tree to be a tree, and not of anything that is not a tree. Hence, our understanding of a thing is separated from its matter and is necessary to it in some respect. Now, what is in motion is not necessary, since what is in motion can change. Thus, the degree to which we have understood something is conditional upon the degree to which it is separated from matter and motion. It follows then that speculative objects, the subject-matter of the speculative-sciences, insofar as they are what are understood, will be separated from matter and motion to some degree. Any distinctions that obtain amongst speculative objects will in turn signify distinctions amongst the sciences that consider those objects; and we can find distinctions amongst speculative objects based upon their disposition towards matter and motion.
There are three divisions that can apply to speculative objects, thereby permitting us to differentiate the sciences that consider such objects: (i) there is a class of speculative objects that are dependent on matter and motion both for their being and for their being understood, for instance, human beings cannot be without matter, and they cannot be understood without their constituent matter (flesh and bones); (ii) there is a class of speculative objects that depend on matter and motion for their being, but not for their being understood, for instance, we can understand lines, numbers, and points without thereby understanding the matter in which they are found, yet such things cannot be without matter; (iii) there is a class of speculative objects that depend on matter and motion neither for their being nor for their being understood.
Given these three classes of speculative objects, the speculative sciences that consider them can be enumerated accordingly: (i) physical science considers those things that depend on matter and motion both for their being and for their being understood; (ii) mathematics considers those things that depend on matter and motion for their being but not for their being understood; [rcolor=red](iii) metaphysics or theology deals with those things that depend on matter and motion neither for their being nor for their being understood.[/color] Before going on to consider the subject-matter of metaphysics in a little more detail, it is important to point out that Thomas takes this division of the speculative sciences as exhaustive. For Thomas, there could be no fourth speculative science; the reason for this is that the subject-matter of such a science would have to be those things that depend on matter and motion for their being understood but not for their being, for all other combinations have been exhausted. Now, if a thing depends on matter and motion for its being understood but not for its being, then matter and motion would be put into its definition, which defines a thing as it exists. But if a thing’s existence is so defined as to include matter and motion, then it follows that it depends on matter and motion for its being; for it cannot be understood to be without matter and motion. Hence, all things that include matter and motion in their definitions are dependent on matter and motion for their being, but not all things that depend on matter and motion for their being depend on matter and motion for their being understood. There could be no fourth speculative science since there is no fourth class of speculative objects depending on matter and motion for their being understood but not for their being. Thomas thus sees this threefold division of the speculative sciences as an exhaustive one.
The third class of speculative objects comprises the objects of metaphysics or theology. Now Thomas does not equate these two disciplines, but goes on to distinguish between the proper subject-matter of metaphysics and the proper subject-matter of theology. Recall that this third class of speculative objects comprises those things depending on matter and motion neither for their being nor for their being understood. Such things are thus immaterial things; however, Thomas here draws a distinction. There are things that are immaterial insofar as they are in themselves complete immaterial substances; God and the angels would be examples of such things. To give the latter a title, let them be called positively immaterial.
On the other hand there are things that are immaterial insofar as they simply do not depend on matter and motion but can nevertheless be sometimes said to be found therein. In other words, things of the latter category are neutral with respect to being found in matter and motion, and hence they are neutrally immaterial. St Thomas’s examples of the latter are being, substance, potency, form, act, one and many; such things can apply equally to material things (such as humans, dogs, cats, mice) and, to some extent, to positively immaterial things. Thus, the neutrally immaterial seem to signify certain aspects or modes of being that can apply equally to material and to immaterial things. The question then arises: what is the proper subject-matter of metaphysics: the positively immaterial or the neutrally immaterial?According to Thomas, unaided human reason cannot have direct knowledge of the positively immaterial; this is because such things (God and angels) outstrip the human intellect’s capacity to know. Nevertheless, direct knowledge of the positively immaterial is possible, but this will not be on the basis of unaided human reason; it will require that the positively immaterial reveal themselves to us in some way, in which case direct knowledge of the positively immaterial will be dependent on some sort of revelation.
As it is a purely rational science, not dependent on or presupposing the truths of revelation, metaphysics will be a study of the neutrally immaterial aspects of things, that is, a study of those modes of being that apply to all beings, whether they are material or immaterial. Such a study will be in accord with the Aristotelian conception of metaphysics as a study of being qua being, insofar as the neutrally immaterial apply to all beings and are not restricted to a certain class of beings. However, Thomas does not adopt the Aristotelian phrase (being qua being) as the subject-matter of metaphysics, he offers his own term. According to Thomas, ens commune (common being) is the proper subject-matter of metaphysics. Through an investigation of ens commune, an investigation into the aspects of being common to all beings, the metaphysician may indeed come to a knowledge of the causes of being and might thereby be led to the affirmation of divine being, but this is only at the end of the metaphysical inquiry, not at the beginning.
Thus, metaphysics for Aquinas is a study of ens commune where this is understood as the common aspects of being without which a thing could not be; it does not presuppose the existence of divine being, and may not even be led to an affirmation of divine being (though Thomas of course offers several highly complex metaphysical arguments for the existence of divine being, but this should not be taken to be essential to the starting point of Thomistic metaphysics).
Metaphysics then is a study of the certain aspects common to all beings; and it is the task of the metaphysician to uncover the aspects of being that are indeed common and without which a thing could not be. There are certain aspects of being that are common insofar as they are generally applicable to all beings, and these are essence and existence; all beings exist and have an essence, hence metaphysics will be primarily concerned with the nature of essence and existence and their relationship to each other. Having completed an investigation into essence and existence, the metaphysician must investigate the aspects of being that are common to particular instances of being; and this will be a study of (i) the composition of substance and accident, and (ii) the composition of matter and form. The format of Thomistic metaphysics then takes a somewhat dyadic structure of descending generality: (i) essence and existence, (ii) substance and accident, (iii) matter and form. The format of the remainder of this article will be an investigation into these dyadic structures.