The aim of the article is to present the role played by the will in human action in the accounts of Thomas Aquinas and John Buridan. The achievements of contemporary analytic philosophy are the context for considering medieval theories of action. First, I focus on second-order volitions whose objects are desires (John Buridan and Harry Frankfurt). Next, I present the modifications of this theory carried out by Thomas Aquinas and Lawrence A. Blum. They agree in postulating some kind of self-cognition as the source of second-order volitions; however, it would seem that Aquinas, who argues for placing the source of such acts in obligation (God’s principles), offers a significant improvement on Blum’s account.