As found in manuals of philosophy, the theory of transcendentals - being, one, true, good - seems a rather simple, quickly-ordered affair; such, in its finished form, it may well be. Historically, however, the course of development was not quick and easy. Progress came gradually, with ensuing complexity; and when the doctrine had achieved maturity, it was the work not of one but of many, successive contributors.
Aristotle states very clearly what is required for a notion to be transcendental, at least so far as it applies to the one, whose thorough identity and convertibility with being he noted to perfection.5 By contrast, Aristotle does not treat of the good in the same metaphysical way, under the aspect of a universal property, so as to show its identity with being. For him the good, to be sure, is everywhere the principle of action, but its assimilation to the order of being never quite materializes. Much the same goes for the true, and for being as true; these are dealt with only in their subjective side, as pertaining to the terminal or perfective phase of the act of knowledge. In this sense the true, as we saw in the preceding chapter, is a property of judgment rather than of being; which explains why the true does not enter Aristotle's philosophy of being, or enters it only to be dismissed.
Actually, the formation of what was to become the standard triad of transcendentals relative to being - the one, the true, the good - was the work of Christian philosophy, in which, moreover, the first conceptions of the triad were mostly theologically inspired. One, true, and good were thought of as attributes of the primary Being, and were referred to each of the three Persons of the Trinity. But in creatures, too, signs or vestiges of these divine attributes were sought. From the beginning of the thirteenth century any number of Summas appeared, as well as Commentaries on the Sentences of Peter Lombard, which testify to this first and largely theological development of the doctrine of transcendentals. Its philosophical elaboration, on the other hand, appears to have been the special contribution of St. Thomas, from whom the doctrine does indeed emerge in definitive form. We have already made reference to his article that is basic to the subject; we proceed now to examine it more closely.
Since being is what the intellect first conceives of anything, all other conceptions must be formed by some addition to this fundamental notion. We have seen, however, that addition to being cannot be made as though to a genus, but rather by expressing various modes not explicitly signified in the mere notion of being. If the modes are particular, they represent predicaments; if universal, they express transcendental being and hence are named "transcendentals."
But on what basis are the universal modes themselves distinguished? First, according as they pertain to being taken absolutely (in itself), or relatively (to another being). In the first case, that of being in itself, the mode expresses something of being either affirmatively or negatively, and these alternatives give rise to two of the transcendental notions. Affirmatively, the only possible attribution to every being is that of its essence, to which corresponds the term "thing" (res) . Negatively, there is also a single predication of being, its undividedness, signified in the term "one" (unum ). "Thing" and "one," accordingly, are the two transcendentals which pertain to being absolutely. On the other hand, being may also be considered relatively, or under the relation of one being to another, which may be a relation of distinction or one of conformity. Being, conceived of as distinct from others, is named aliquid, "something," as though to say "some other thing." It is easy to see that every being is distinct from every other being, but how can every being be conformed or assimilated to some other being? This is possible only if there is a being to which every other being is somehow accommodated. Such is the human soul, which by its powers of knowledge and appetition enjoys this amplitude. The accommodation or correspondence of being to the powers of knowledge is expressed by the term "true" (verum); whereas the accommodation to the powers of appetition is expressed by the "good" (bonum). In short, then, three things may be said of every being taken relatively: true, good, and otherness (some other thing). With that, all the transcendentals are accounted for. On this capital point, however, we ought to hear St. Thomas again, this time in full: This mode [common and consequent upon every being] can be taken in two ways: first, as following upon every being considered absolutely; second, as following upon every being considered in relation to another. In the first, the term is used in two ways, because it expresses something in the being either affirmatively or negatively. However, 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 the essence of the being. As for the negation consequent upon every being considered absolutely, this is its undividedness, which is expressed by one; for the one is simply undivided being.
If the mode of being is taken in the second way - according to the relation of one being to another - we find a twofold use. The first is based on the distinction of one being from another, and this distinctness is expressed by the word something (aliquid), which implies, as it were, some other thing. For, just as being is said to be one in so far as it is without division in itself, so it is said to be something in so far as it is divided from others. The second division is based on the correspondence one being has with another. This is possible only if there is something which is such that it agrees with every being. Such a being is the soul, which "in some way is all things," as is said in the treatise On the Soul [111,8, 431 b 21]. The soul, however, has both knowing and appetitive powers. Good expresses the correspondence of being to the appetitive power. . . . True expresses the correspondence of being to the knowing power... .' As readily seen, St. Thomas in this passage lists, besides being itself, five transcendental notions: thing, one, something, true, good - res, unum, aliquid, verum, bonum. The term "thing," however, does not, it seems, say anything that is not explicitly said by the notion of being, for it does no more than express the aspect of essence in things; some authors, as a matter of fact, do not consider it a transcendental property in the truest sense. As for "something," it can be interpreted two ways. Either it denotes the opposition or distinction of one being to another, and then it may be regarded as a consequence of the unity of being; or it marks the opposition of being to nonbeing - namely, that being is something other than nonbeing - , in which case it expresses an original and primary aspect of being. Yet granted the authenticity of "thing" and "something" as transcendental properties of being, it is doubtful that they command the same philosophical interest as does the triad of the one, the true, the good, deservedly recognized as the classical three. To them, modern authors like to add the "beautiful" (pulchrum), which does indeed appear to be an aspect of all being. But though it denotes the agreement of being with the soul, it does so through the conjoint powers of knowledge and appetition; hence, instead of a primary transcendental it is more properly deemed a derivative one.