Tractatus de divina traditione et Scriptura

1. The internal reason in some truths shines forth immediately from the perceived terms themselves. There are namely truths in which either every intellect in possession of itself, or at least one somewhat more cultivated, sufficiently perceives by an easy intuition the comprehension of the notes in the one and the other idea — which are compared and are the terms of the judgment and of the proposition — so that from the very perceived notion their agreement or disagreement is immediately evident to it. Evident in this way to any intellect whatever are those truths whose elements are the most universal ideas, and therefore simplest in comprehension of notes, which the intellect first forms as it goes forth into act. These are the first principles, from which the intellect advances to understanding other things. Whence it appears why the simply first principle for us (in the logical order) is this: « that the same thing cannot at once be and not be. » For in the idea of being, which the intellect forms first of all, this principle is founded, and from it is immediately understood; in it, moreover, all subsequent cognitions are founded. For all subsequent concepts are formed by addition to being taken most universally and therefore most abstractly — not indeed by addition of something which is outside the character of being, outside of which there is nothing, but through a more express conception of the modes which effect all being (thing, one, something, true, good), or through the conception of the grades of being according to which there are the diverse genera of things. See S. Th. de Verit. q. 1. a. 1. θ.

Because the light of the intellect, or the intellectual power connatural to us, connaturally forms such fundamental concepts and first principles without study and the culture of discipline, as soon as it puts itself forth into its own proper acts, and because all subsequent activity connatural to the intellect advances from those first principles, they are therefore called principles innate in us. « There pre-exist in us certain seeds of the sciences, namely the first conceptions of the intellect, which are known at once by the light of the agent intellect through species abstracted from sensibles, whether they be complex as dignities (ἀξιώματα or principles), or incomplex as the character of being, of one, and the like, which the intellect apprehends at once. From these universal principles, moreover, all principles follow as from certain seminal reasons » S. Th. de Verit. q. 11. (de Magistro) a. 1. cf. q. 10. a. 6.

2. Sometimes the ideas to be compared, or the terms of the judgment and of the proposition, are sufficiently perceived according to their notes not by any intellect in possession of itself, but only by an intellect already preformed and cultivated by many notions, so that from the perceived terms themselves their agreement or disagreement is evidently understood. Truths of this kind, immediately evident not to all but only to the learned, are many in all disciplines.

Both classes of truths which are self-evident St. Thomas sets forth. « As Boethius says, some are dignities (ἀξιώματα) or propositions self-evident commonly to all, and of this kind are those propositions whose terms are known to all... But some propositions are self-evident to the wise alone, who understand what the terms of the propositions signify... In those things, moreover, which fall into the apprehension of men, a certain order is found. For that which first falls into apprehension is being, whose understanding is included in all things whatsoever one apprehends; and therefore the first indemonstrable principle is that it is not at once to affirm and to deny, which is founded upon the character of being and non-being, and upon this principle all others are founded » S. Th. 1. 2. q. 94. a. 2.

3. In truths which are understood from the perceived terms themselves, or which are self-evident, the material object (which is manifested to the intellect and which is known) is also the formal object (under which it is manifested and known); they are therefore rightly called truths known through themselves. Nevertheless even in these the material and formal object can be distinguished by the reason and consideration of the mind.

The cognition of truth manifested through itself, or self-evident, is, as is clear, immediate cognition, and this is specifically called intellection or intellect by the ancients in distinction from science (of which presently); whence they say: intellect is of principles. Hence also the faculty of the mind, or the mind itself insofar as it is referred to the intuition of self-evident truth, is called intellect in distinction from reason, which is referred to the science of truths known from others as from principles.

Corollary. When simply and without qualification we speak of self-evident truths, we mean truths self-evident for our human intellect. In themselves all necessary truths would be self-evident; for with the quiddity of the terms sufficiently understood, the agreement or disagreement of the same would thereby be understood. But when the human intellect does not sufficiently penetrate the quiddity of the terms, it comes about that neither can it understand the agreement and disagreement from the terms themselves; and thus truths of this kind for us are not self-evident. S. Th. de Verit. q. 10. a. 12.