This is an important principle, often laid down as follows: -- God knows His own nature in all the various modes in which that nature can be copied outside Himself In knowing this, He knows the ideal order, every detail and all inter-relations of details in any possible universe. This is called the knowledge of simple understanding, inasmuch as it is the knowledge of all creatable creatures and their ongoings, antecedent to and apart from the creation and actual existence of any: this knowledge however dwells only in the ideal order of possibilities, and may therefore be called general and universal, though not abstract, inasmuch as it deals with types of individual things, but not with particular existences in rerum natura as actually existing, but only as potentialities. God further knows things outside Himself as they actually and individually exist, inasmuch as all things are of His causation and creation, and exist and act under His will and power. He knows them by insight of Himself, not as He is a mere nature, but as He is a nature willing to create on these particular lines. This knowledge of the universe as the universe actually is for all time, is called the knowledge of vision. For these two knowledges sec Chap. LXVI. The knowledge of simple understanding is not abstract, inasmuch as God knows, not only types of species, but types of different individuals possible in each species; and all these several types He knows, not by so many several ideas, but in the one act by which He knows Himself.

Of God and His Creatures: 1.50