a) To the study of being as being Aristotle joins the study of certain primary truths which he names 'axioms.' 22 The reason is clearly stated; these truths, he says, should be studied in the science of being because they have the same amplitude or universality as being. "Since," in his own words, "it is evident that the axioms hold good for all beings as beings . . . he who studies being as being should also take account of them." 23
In line with this recommendation of Aristotle's, many metaphysical authors in his tradition take up first principles immediately after their treatment of being as such. Others, it is true, consign this topic to logic, pleading that these principles are the basic laws which govern every exercise of reason. That they do so govern is unquestionable; yet prior to their directive function over the mind is their operation as objective laws of being, and it is in the latter capacity that they are first as well as immediately made known to us. Hence, to couple the consideration of these primary truths with the study of being as being is, as Aristotle plainly shows, the proper course of inquiry. The consideration, moreover, which is calculated to assure the mind of all first truths, falls naturally within the scheme of the present chapter, that is, within the context of the critical study of being and of the first foundations of our knowledge. Yes, in the matter of first principles metaphysics and critique (criteriology) are practically equivalent. b) To start off, we should be clear as to the meaning of first principle. Generally speaking first principles, as the name implies, are something primary or ultimate. Working backward (Scholastically: "in the ascending order"), they represent the final or ultimate link in the chain of knowledge, the last limit beyond which the resolution of knowledge cannot go. As a rule the expression "first principles" refers to judgments or propositions, but St. Thomas also applies it to the terms or concepts, the elements as it were, of a proposition. We shall restrict our inquiry to the first meaning, to principles in the form of propositions. Also, it should be obvious that in the study of being and its first principles we have not to concern ourselves with principles that are special to any science but only with those that pertain to all being and so are absolutely common - common to each and every science.
Considered in themselves first principles must be not only true and necessary, as a matter of course, but also immediate (Scholastically: per se nota). Immediacy, as applied to a principle, means that the truth of it is understood without the help of intermediate notions or middle terms. We have only to grasp the meaning of the terms that make up the principle, and the truth of the proposition becomes instantly evident. In this sense first principles are said to be self-evident or known through themselves, the literal rendering of per se nota. When, moreover, a principle is absolutely first, the terms it comprises must also be absolutely first or simple, hence incapable of reduction to prior notions. If they could be reduced, they would not be first. Every science has its principles, which may not be absolutely first. Even then, however, the principles, as the name indicates, are basic points of reference for the science; the science rests on them and every development necessarily implies and presupposes them. As for the metaphysical principles relating to being, these are first to all others, so that all knowledge of whatever order is subordinate to them. Hence the capital importance of these first or primary truths.
c) Which among the metaphysical principles just referred to comes before all others? Thomists today do not agree. For Aristotle, on the other hand, the question was settled.24 This principle, he argued, would have to meet three conditions; it must be i)the best known, 2)the first known, and 3)the most certain, "about which it is impossible to be mistaken." Which is this principle? For Aristotle it is unequivocally the principle of noncontradiction - or, elliptically, "of contradiction." 25
1. The Principle of Noncontradiction
a) The formulation of the principle varies. Aristotle proposes, without preliminaries, the following: "it is impossible that the same attribute belong and at the same time not belong to the same subject in the same respect." St. Thomas' rendition of this is:
impossibile est eidem simul inesse et non inesse idem secundum idem,which in English comes to: "it is impossible to affirm and to deny the same thing at the same time in the same respect."
So formulated, the immediate reference of the principle of noncontradiction is to operations of the mind, to attribution and nonattribution (i.e. affirmation and negation), which are declared mutually exclusive under the conditions of the principle. A more metaphysically-oriented formulation can be made, seeing that in any judgment - we are dealing with principles that are judgments - the mind is determined by the reality which serves as its object. For example, I judge that the sky is blue because I see that it is actually blue. Consequently, it is more conformable even to the structure of knowledge to word the principle with a view to its objective content, in which case it will read "being is not nonbeing," or, same sense, "what is, is not what is not." So, to follow our usual practice, we have in Latin:
ens non est non ens.
In metaphysics, evidently, where our standpoint is that of objective being, the preferred formulation should be the objective one, "being is not nonbeing" or its aforementioned variant.
b) Next, we examine the steps by which the mind becomes cognizant of the principle. Plainly, the principle results from comparing and contrasting two notions, "being" and "nonbeing." The being here in question is none other than that first datum of the intellect of which we spoke in the preceding chapter. As for the notion of nonbeing, the mind sees at once that its positive content is again the notion of being, from which it but differs by the negation it bears, solely an act of the mind. This response of the mind to the conception of being, the negation of it, is absolutely primary, a comportment so basic and instinctive to the mind that there is no way of defining it except through itself. The mind, accordingly, first apprehends (and conceives) being; then it denies (or conceives the negation of) being; and thus it has the notion, or the pseudo-notion, of nonbeing.
Comparing the notions of being and nonbeing, we see and cannot fail to see that they are irreducible to each other. The recognition of their incompatibility is immediate and necessary, a primordial datum of the mind. Being, as being, can never be nonbeing. In consequence of this opposition, which is absolute and irresoluble, it is impossible - and this was our first formulation of the principle - to both affirm and deny the same thing at the same time and in the same respect. Such simultaneous affirmation and denial would in effect identify being with nonbeing, and this the mind is utterly incapable of doing - the mind, I say, because the speech of man can say even what the mind cannot. All told, then, in the discovery of the principle of noncontradiction the mind employs but one positive notion, that of being, upon the conception of which it posits two successive acts of negation, negation of being and of compatibility between being and nonbeing. This done, it only remains to give verbal expression to the objective incompatibility thus discovered.
c) Having seen how the mind arrives at the principle of noncontradiction, we come to the question of its validity, or the grounds for asserting its validity. That the principle is an absolute, objective truth is immediately or self-evident; as soon as the mind grasps the notion of being and nonbeing it necessarily recognizes their mutual exclusivity as well as the absolute character of the exclusion; and this, in essence, is the principle. But is there another way, or rather a way - since what is self-evident is not proved - to justify and certify the principle? A direct demonstration is obviously out of the question, for this would needs be based on the apprehension of a prior truth, the impossibility of which is clear from the fact that nothing is prior to being. But what of an indirect demonstration, the refutation by absurdity? In general, refutation by absurdity consists in showing that a certain proposition necessarily involves the holder in contradiction; he is saying what he is not saying, or not saying what he is saying. In the present instance such a maneuver would be beside the point, since the possibility of contradiction - the possibility of contradicting the principle - is precisely what its adversary maintains. (Note again that what is at stake is not the possibility of mouthing a contradiction but the possibility of thinking it, or thinking it true.)
In our case, then, the adversary, if he is to be met on his own grounds, is not trapped by confronting him with his contradiction of himself but by reducing him to silence. To affirm the identity of contradictories, in other words, is no longer to have a distinct object of thought; it is to have no thought at all. Thus, if the adversary concedes that he has some definite thing in mind and thereby attaches some meaning to the word that expresses his thought, he automatically acknowledges that being is not contradictory; he either has an object of thought or not, either means something or does not. If, in spite of this, he sticks to his oral denial of the principle, the denial is a mere trick of words, deprived of anything distinguishable as an object of thought. The alternatives here are to think of something or not to think at all; there is no other possibility. In sum, if you wish to think you must fix on some determined object; you must, that is, acknowledge the dictates of being.
d) A final word pertains to the extent of the principle's applicability. Since it originates from the notion of being, the principle, taken in itself and unrestrictedly, holds good for all modes of being, which is simply to say for all being; and, correlatively, it holds good for all thought relating to being, which is again to say for all thought, as this always relates to being of some kind. However, the beings of our experience, because they are many and variable, are none of them endowed with the fullness of being. While in some respects they are indeed being, in other respects they are nonbeing - there is being which is not their being. Consequently, the principle of noncontradiction applies to such beings but from certain points of view and within certain limits; what it says in effect is that so far as they are being, they are not nonbeing. Only for absolute being, which is God, does the principle hold in absolute manner.
2. The Principle of Identity
Modern philosophers, Scholastics included, speak of yet another, an affirmative principle which is thought to go with the principle of noncontradiction and by some is even placed ahead of it. This is the principle of identity, by which being is predicated of itself.
a) St. Thomas, for his part, makes no mention of this principle, at least not in so many words. When, in logic or in metaphysics, he treats of the axioms, the primary truths, nothing is ever said about this one. Nevertheless, something akin to the principle, or even its equivalent, can be traced in his thought. For one thing, St. Thomas does speak of identity and tells us very exactly what he means by it, namely, the mode of unity proper to substance. Hence, to affirm the identity of being would, in a way, be the same as to assert its unity. Thus understood, the principle of identity would but come to another expression for what might be called the principle of unity of being: that every being is one, or identical with itself. Of this, of course, there can be no doubt. That every being is one or identical with itself is a very true proposition, and a very accurate one at that - known, moreover, with all the immediacy of a first principle. However, in introducing the notion of the transcendental one, the proposition goes beyond the mere notion of being, and this, it is agreed, the principle of identity must not do. Consequently, if the principle is to have a formal basis in St. Thomas, recourse must be had to some other doctrinal context, which, we believe, is provided in the following passage:
One cannot find anything that is predicated affirmatively and absolutely of every being except its essence, according to which it is said to be, and is given the name "thing" (res). For, as Avicenna explains [Metaph.I,6], "thing" differs from "being" (ens) in this, that being is named after the act of existing [ab actu essendi], whereas thing expresses the quiddity or essence of the being.26
In the distinction made in this text we find the clue to the principle of identity, such as accords with the thought of St. Thomas.
b) It is at once clear that unless the predicate differs somehow from the subject, there can be no judgment in the true sense of the word. A strictly tautological predication of being (where "being" is used twice with the identical meaning) constitutes no judgment at all. Thus, "being is being" tells us nothing unless the second "being" enlarges, however modestly, upon the first. And here enters a problem. Being, it is obvious, must be the subject of any statement of the principle of identity; yet being signifies everything. Where, then, find a predicate that will add anything to the signification of the subject? St. Thomas, as we have said, points the way in the above citation, making within being itself the distinction, now familiar, of being as existent and being as essence. The principle, accordingly, comes to "being (as existent) is being (as essence)."
Authors are agreed that this is the general sense of the principle, even though in their explication of it some differences appear. If the principle is thought to accentuate the distinction between essence or thing (res) and the act of existing, then the reading of it might well be, as Garrigou- Lagrange proposes, "every being is something determinate, something of a determinate nature which constitutes it in its proper self." 27 In short, every being has a certain nature. On the other hand, it would seem preferable to keep the formulation of the principle more strictly within the limits of the notion "what exists" (ens), namely, by considering essence not as a certain essence but as the essence of being itself. Thus, instead of, Is being something determinate? the question would be, What thing, what nature is being? and the reply (the principle), It is being. In other words, "every being is what it is," as Maritain phrases it; 28 or simply, "being is being" - ens est ens - , which says in effect "being has for nature to be." These latter formulas win our acceptance, for the reason that they keep closer to the mind's original discovery of being - closer than formulations which, like that of Pere Garrigou-Lagrange, single out the determination being receives from essence (res). c) Concerning some other aspects of the principle, we have only to repeat what was said apropos of the principle of noncontradiction. In both, the mind, affirming or denying, expresses itself as it does only because it sees the objective agreement or nonagreement, as the case may be, between the two terms involved, between subject and predicate. Furthermore, like the principle of noncontradiction, that of identity is coextensive with being; it holds for all being. Again, however, it holds proportionately: for limited or imperfect beings, only so far as they are (in some respects, it will be recalled, they are not). To God, on the other hand, and only to him it applies simply; for, as he alone is being absolutely, so he alone is being identically. d) There remains one question. To which principle should the primacy go, to identity or noncontradiction? Objectively speaking, or from the view of notional content, both presuppose but one (and that the same) datum, namely being; and both terminate in the same object, again being. Each of them, moreover, is immediate or self-evident; nor is the truth of one subordinate to the truth of the other. On the subjective side (the side of mental activity), a difference is more easily found: two acts of negation in the one (noncontradiction); discrimination of essence and existence and an act of affirmation in the other (identity). From this point of view it is perhaps possible to speak of (psychological or logical) priority. In metaphysics, however, since neither principle goes beyond the explicit content of the notion of being, the question of priority has not to be raised.
3. Other Principles
Together with the principle of noncontradiction Aristotle discusses an immediate consequence of it, "that between the affirmation and negation of being no middle ground is possible; that being is or is not." This is commonly known as the law of excluded middle, and the mention of it shall suffice. Modern authors include for discussion at this point a number of other principles: principle of sufficient reason, of causality, of finality, of substance. These principles are certainly essential to the mind in its manifold work of inquiry; but, considering that they deal with notions and distinctions which, in regular procedure, have not been met with at this stage of metaphysical study, it is more logical to speak of them later. We shall keep to this more methodical course and in the next chapter go at once to the properties of being, that is, the properties other than being itself considered as "quiddity" and in its opposition to nonbeing.
Concluding note: On the origin and formation of first principles. These principles are not innate; they are not known prior to all experience. What is innate is the power to know them, the intellect, which at first has no actual knowledge whatever, though it is in potency, pure potency, to every intelligible. Knowledge of first principles, specifically of the ones studied above, is acquired in the same way as other knowledge, through the senses. From the presentations of sense the intellect abstracts the notion of being;
once this notion is formed the principles are formed, immediately. Our first recognition of them, however, comes from particular cases, from this or that being; not until being is grasped in its universality are the principles formulated in their universality.
While not innate, first principles are nevertheless said to be natural to our intellect, in the sense that they are a necessary, never-failing consequent of its operation; thus, if the intellect acts at all, it cannot but be in possession of them. In the human intellect, moreover, they serve as a kind of habit (habitus), a stable disposition which enables a faculty to function more readily and more dependably. This habit, furthermore, is twofold, according as the principles pertain to the speculative order or to practical action. In metaphysics, keep in mind, we are concerned with first principles of the speculative order; not innate, they nevertheless perfect the intellect naturally rather than by deliberate cultivation.29