3. As God by knowing His own being knows the being of everything, so by knowing His own act of understanding and will He knows every thought and volition.
5. God knows intelligent substances not less well than He knows or we know sensible substances, seeing that intelligent substances are more knowable, as being better actualised. This is confirmed by the testimony of Holy Scripture: -- God searcher of hearts and reins (Ps. vii, 10): Hell and perdition are before the Lord: how much more the hearts of the sons of men? (Prov. xi, 11): He needed not that any one should bear testimony of what was in man: for he himself knew what was in man (John ii, 25).
The dominion of the will over its own acts, whereby it has it in its power to will and not to will, is inconsistent with will-force being determined to one fixed mode of action: it is inconsistent also with the violent interference of any external agency; but it is not inconsistent with the influence of that Higher Cause, from whence it is given to the will both to be and to act. And thus in the First Cause, that is, in God, there remains a causal influence over the motions of the will, such that, in knowing Himself, God is able to know these motions.*
1.67 : That God knows Individual Contingent Events
1.69 : That God knows Infinite Things