St. Thomas's Question 83, Article 1

If you look at prima-pars, question 83, Article 1, St. Thomas says, free will is the cause of its own movement because by his free will, man moves himself to act. He continues, but it does not of necessity belong to liberty, that what is free should be the first cause of itself. God, therefore, is the first cause. Who moves causes both naturally and voluntary. So here, he's coming back with much of the same sort of languages we saw before.