Abstract

Saint Thomas Aquinas establishes why is it that logic is the directive art of the act of reason and why is it convenient to divide it in correspondence with the operations of the intelect. Thus, the Posterior Analytics are related with the act of reason which goes from one thing which is known to other thing that is unknown. By analogy with the process of necessity of nature, in which she can not fail, Aquinas explains that truth can not fail in the demonstrative syllogism, which has the certainty of science, and that this act of reason is founded in the Posterior Analytics. The rest of saint Thomas Aquinas' exposition focuses on determining to which books of logic does each act or process of reason corresponds.