As one of the leading intellectual figures of the Middle Ages, Aquinas was a Dominican master in theology who taught at the University of Paris (1256–59 and 1268–72), as well as in Dominican schools of Rome (1265–68) and Naples (1272–74). Following the impetus of his master Albert the Great (1206–80), he is responsible for having integrated into Christian thought philosophical themes found in Aristotle's Nicomachean Ethics, Metaphysics, On the Soul, and Physics, which were made available for the first time in Latin translations in the thirteenth century. Aquinas's grand synthesis of Aristotelianism and Christianity was extremely influential, so much so that Descartes had to be especially careful, four centuries later, not to offend the church when trying to replace Aristotelianism with his own philosophical ideas.

The influence of the Summa Theologica (1268–73), Aquinas's magnum opus, was felt up through the seventeenth century. Along with Aristotle's thought, Aquinas's work undergirded the educational system of the Jesuit schools in this period. Even at the threshold of the modern age, his work was the object of voluminous Jesuit commentaries, including those by Francisco Suárez.

Descartes rarely invokes the name of Aquinas in his writings, although he indicates in his correspondence (AT II 630, CSMK 142) that he possesses a “Summa” (presumably the Summa Theologica). And when the official objectors to the Meditations compelled him to compare his arguments with those of the Angelic Doctor, Descartes seems anxious to avoid direct criticism (as in the First Replies). But in developing his own doctrine he never ceases to struggle with Aristotelian themes, as reworked and elaborated by Aquinas. Three areas of particular concern are knowledge, metaphysics, and physics. With respect to the first, Descartes gives the theory of knowledge a primacy not found in either Aristotle or Aquinas. He also seeks to undermine the Thomistic empiricist dictum that “nothing is in the intellect unless it was first in the senses” (nihil est in intellectu nisi prius fuerit in sensu) and to develop a system of true knowledge obtained by withdrawing the mind from the senses (AT VII 9, CSM II 8). In metaphysics, the battle is fought over the concepts of substance and accident.