Answer :
In Summas Theologica, Aquinas argues that the law of negation is how one can understand God.
Explanation:
Law of Negation according to Aquinas states that humans understand anything by negating possibilities of what it could be and what it is not.
In the same way we can understand what God is by making sure what God is not and what God cannot be.
He argues that
God does not exist in Time,
God is not changeable
and God is not made up of parts.
These are the core arguments through which one is to understand what God is.