In the Father there must be a real relation to the Son and to the Holy Ghost. Hence, corresponding to the two relations of the Son and of the Holy Ghost, whereby they are related to the Father, we must understand two relations in the Father, whereby He is related to the Son and to the Holy Ghost. Hence, since there is only one Person of the Father, it is necessary that the relations should be separately signified in the abstract; and these are what we mean by properties and notions.
The use of concrete and abstract names in God is not in any way repugnant to the divine simplicity; forasmuch as we always name a thing as we understand it. Now, our intellect cannot attain to the absolute simplicity of the divine essence, considered in itself, and therefore, our human intellect apprehends and names divine things, according to its own mode, that is in so far as they are found in sensible objects, whence its knowledge is derived. In these things we use abstract terms to signify simple forms; and to signify subsistent things we use concrete terms. Hence also we signify divine things, as above stated, by abstract names, to express their simplicity; whereas, to express their subsistence and completeness, we use concrete names.
But not only must essential names be signified in the abstract and in the concrete, as when we say Deity and God; or wisdom and wise; but the same applies to the personal names, so that we may say paternity and Father.
RO2: In God the notions have their significance not after the manner of realities, but by way of certain ideas whereby the persons are known; although in God these notions or relations are real (Q28, A1). Therefore whatever has order to any essential or personal act, cannot be applied to the notions; forasmuch as this is against their mode of signification. Hence we cannot say that paternity begets, or creates, or is wise, or is intelligent. The essentials, however, which are not ordered to any act, but simply remove created conditions from God, can be predicated of the notions; for we can say that paternity is eternal, or immense, or such like. So also on account of the real identity, substantive terms, whether personal or essential, can be predicated of the notions; for we can say that paternity is God, and that paternity is the Father.