Chapter 2.—God the Only Unchangeable Essence.
3. He is, however, without doubt, a substance, or, if it be better so to call it, an essence, which the Greeks call οὐσία. For as wisdom is so called from the being wise, and knowledge from knowing; so from being559 John i. 1, 14 Esse 1 Cor. i. 24 comes that which we call essence. And who is there that is, more than He who said to His servant Moses, “I am that I am;” and, “Thus shall thou say unto the children of Israel, He who is hath sent me unto you?”560 [This singleness and doubleness is explained in chapter 3.—W.G.T.S.] Ex. iii. 14 But other things that are called essences or substances admit of accidents, whereby a change, whether great or small, is produced in them. But there can be no accident of this kind in respect to God; and therefore He who is God is the only unchangeable substance or essence, to whom certainly being itself, whence comes the name of essence, most especially and most truly belongs. For that which is changed does not retain its own being; and that which can be changed, although it be not actually changed, is able not to be that which it had been; and hence that which not only is not changed, but also cannot at all be changed, alone falls most truly, without difficulty or hesitation, under the category of being.
CAPUT II.
3. Deus sola incommutabilis essentia. Est tamen sine dubitatione substantia, vel, si melius hoc appellatur, essentia, quam Graeci οὐσίαν vocant. Sicut enim ab eo quod est sapere dicta est sapientia, et ab eo quod est scire dicta est scientia; ita ab eo quod est esse dicta est essentia. Et quis magis est, quam ille qui dixit famulo suo Moysi, Ego sum qui sum; et, Dices filiis Israel: Qui est, misit me ad vos (Exod. III, 14)? Sed aliae quae dicuntur essentiae sive substantiae, capiunt accidentia, quibus in eis fiat vel magna vel quantacumque mutatio: Deo autem aliquid ejusmodi accidere non potest; et ideo sola est incommutabilis substantia vel essentia, qui Deus est, cui profectio ipsum esse, unde essentia nominata est, maxime ac verissime competit. Quod enim mutatur, non servat ipsum esse; et quod mutari potest, etiamsi non mutetur, potest quod fuerat non esse: ac per hoc illud solum quod non tantum non mutatur, verum etiam mutari omnino non potest, sine scrupulo occurrit quod verissime dicatur esse.