In this paper we study the conception about the agent intellect of Alfonso, Bishop of Toledo. This thinker criticizes three systems of philosophy: a) The averroism, hypothesis which sustains the identification between the agent intellect with God. b) The potentialism, opinion of those who think that the agent intellect is a potency. c) The nominalism, position of those who defend that there is no real difference between the agent and the possible intellect. This author defends the habitualism, thesis that identifies the agent intellect with an innate habit, concretely, with the habit of first principles.