Now God differs from God in no respect, for there cannot be divine essences distinguished either by accidents or by substantial differences belonging to a substrate. But where there is no difference, there is no sort of plurality and accordingly no number; here, therefore, is unity alone. For whereas we say God thrice when we name the Father, Son, and Holy Spirit, these three unities do not produce a plurality of number in their own essences, if we think of what we count instead of what we count with. For in the case of abstract number a repetition of single items does produce plurality; but in the case of concrete number the repetition and plural use of single items does not by any means produce numerical difference in the objects counted. There are as a fact two kinds of number. There is the number with which we count (abstract) and the number inherent in the things counted (concrete). "One" is a thing-- the thing counted. Unity is that by which oneness is denoted. Again "two" belongs to the class of things as men or stones; but not so duality; duality is merely that whereby two men or two stones are denoted; and so on. Therefore a repetition of unities[17] produces plurality when it is a question of abstract, but not when it is a question of concrete things, as, for example, if I say of one and the same thing, "one sword, one brand, one blade."[18] It is easy to see that each of these names denotes a sword; I am not numbering unities but simply repeating one thing, and in saying "sword, brand, blade," I reiterate the one thing and do not enumerate several different things any more than I produce three suns instead of merely mentioning one thing thrice when I say "Sun, Sun, Sun." So then if God be predicated thrice of Father, Son, and Holy Spirit, the threefold predication does not result in plural number. The risk of that, as has been said, attends only on those who distinguish Them according to merit. But Catholic Christians, allowing no difference of merit in God, assuming Him to be Pure Form and believing Him to be nothing else than His own essence, rightly regard the statement "the Father is God, the Son is God, the Holy Spirit is God, and this Trinity is one God," not as an enumeration of different things but as a reiteration of one and the same thing, like the statement, "blade and brand are one sword" or "sun, sun, and sun are one sun."