Catechism of the Catholic Church §306 — excerpt
God is the sovereign master of his plan. But to carry it out he also makes use of his creatures' co-operation. This use is not a sign of weakness, but rather a token of almighty God's greatness and goodness.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.