When the existence of a thing has been ascertained there remains the further question of the manner of its existence, in order that we may know its essence.
Now, because we cannot know what God is, but rather what He is not, we have no means for considering how God is, but rather how He is not.
Therefore, we must consider: (1) How He is not; (2) How He is known by us; (3) How He is named.
Now it can be shown how God is not, by denying Him whatever is opposed to the idea of Him, viz. composition, motion, and the like.
Therefore (1) we must discuss His simplicity, whereby we deny composition in Him; and because whatever is simple in material things is imperfect and a part of something else, we shall discuss (2) His perfection; (3) His infinity; (4) His immutability; (5) His unity.
Concerning His simplicity, there are eight points of inquiry:
A Whether God is a body?
A Whether He is composed of matter and form?
A Whether in Him there is composition of quiddity, essence or nature, and subject?
A Whether He is composed of essence and existence?
A Whether He is composed of genus and difference?
A Whether He is composed of subject and accident?
A Whether He is in any way composite, or wholly simple?
A Whether He enters into composition with other things?