 If pressed for more details about how God by His merciful will (uncreated grace) moves a human being to will a particular good, while yet leaving it up to the human being whether he or she wills that good, Arnauld would surely say that we human beings cannot understand God’s causality well enough to supply such details. Our inability to understand God’s causality with regard to the created world is a common theme in Arnauld. It is expressed forcefully in his first contribution to the Leibniz-Arnauld exchange, written in 1686, not long after Liberté. Arnauld says that although we are certain that God, “by a single and very simple act, which is His essence,” knows all things, including things that might not have been, and wills things that He might not have willed by His will, which is also His essence, nevertheless we cannot understand how God does these things, because “as far as we are concerned (à notre égard) God dwells in inaccessible light” (LA, p.  31–32).[41]