Thank you for subscribing to Annotated Thomist...check back each day for a new section of St. Thomas' corpus, annotated and summarized. (FREE TRIAL FOR NEW SUBSCRIBERS!!!)
AT is also available to donors of $10 or more on Patreon along with all of the other benefits (daily bonus videos, bonus articles, PDFs, etc.
If you need more personalized help reading the Summa, I am available for 1-on-1 sessions, here.
cf., Sent.I.D4.Q1.A2, Sent.I.D5.Q1.A2
As we must recall from before, due to the weakness of our intellects and the eminence of the Deity, we often have to switch back and forth between concrete names (e.g., God) and abstract names (e.g., Deity), at times indicating the supreme simplicity of God, and at other times the concrete subsistence.
In the fourth and fifth articles, we ask whether these names can be predicated of the persons in particular, i.e., can we say "the Father is God" (A. 5) or "the Father is the Deity" (A. 6).
Now, from scripture and tradition, it is obvious that we can name each person by the concrete essential name. Thus, we can certainly call the Father "God" and the Son "God."