CHAPTER XIV—That in order to a Knowledge of God we must use the Method of Negative Differentiation³⁰³⁰‘Negative differentiation,’ the chapter will explain the phrase. In St Thomas it is remotio.

AFTER showing that there is a First Being, whom we call God, we must enquire into the conditions of His existence. We must use the method of negative differentiation, particularly in the consideration of the divine substance. For the divine substance, by its immensity, transcends every form that our intellect can realise; and thus we cannot apprehend it by knowing what it is, but we have some sort of knowledge of it by knowing what it is not.³¹³¹   St Gregory Nazianzen, in one of his poems, calls God “one and all things and nothing.”
   In the Summa Theologica, B. I, q. 13, art. 2, St Thomas guards his statement thus: “Of the names that are predicated of God absolutely and affirmatively, as ‘good,’ ‘wise,’ and the like, some have said that all such names are invented rather to remove something from God than to posit anything in Him. . . . . But this account is unsatisfactory. . . . And therefore we must say otherwise, that such names do signify the divine substance . . . . but fail to represent it perfectly. . . . None of them is a perfect expression of the substance of God, but each of them signifies it imperfectly, as creatures also represent it imperfectly.” The more we can negatively differentiate it, or the more attributes we can strike off from it in our mind, the more we approach to a knowledge of it: for we know each thing more perfectly, the fuller view we have of its differences as compared with other things; for each thing has in itself a proper being, distinct from all others. Hence in dealing with things that we can define, we first place them in some genus, by which we know in general what the thing is; and afterwards we add the differentias whereby the thing is distinguished from other things; and thus is achieved a complete knowledge of the substance of the thing. But because in the study of the divine substance we cannot fix upon anything for a genus (Chap. XXV), nor can we mark that substance off from other things by affirmative differentias, we must determine it by negative differentias. In affirmative differentias one limits the extension of another, and brings us nearer to a complete designation of the thing under enquiry, inasmuch as it makes that thing differ from more and more things. And the same holds good also of negative differentias. For example, we may say that God is not an accident, in that He is distinguished from all accidents; then if we add that He is not a body, we shall further distinguish Him from some substances; and so in order by such negations He will be further distinguished from everything besides Himself; and then there will be a proper notion of His substance, when He shall be known as distinct from all. Still it will not be a perfect knowledge, because He will not be known for what He is in Himself.³²³²Not every notion can be absolutely denied of God, as ’spirit,’ ‘power,’ ‘wise,’ ‘just.’ Although He is none of these things in a purely human sense, He is all of them in a more excellent way.

To proceed therefore in the knowledge of God by way of negative differentiation, let us take as a principle what has been shown in a previous chapter, that God is altogether immovable, which is confirmed also by the authority of Holy Scripture. For it is said: I am the Lord and change not (Mal. iii, 6); With whom there is no change (James i, 17); God is not as man, that he should change (Num. xxiii, 19).³³³³St Thomas passes from ‘immovable’ to ‘immutable.’ Aristotle (Physics, vii, 2), distinguishes three sorts of ‘motion’: ‘local motion’ (now the subject matter of dynamics); ‘change,’ or ‘motion in quality’ (now the matter of chemistry); ‘growth and decay,’ or ‘motion in quantity’ (matter of biology). Thus three incongruous things were labelled with one name, to the prejudice of science for many centuries.