section_path: Philosophical views/Thomas Aquinas
section_name: Thomas Aquinas
paragraph_text: Thomas Aquinas
  
  Following Aristotle (whom he referred to as "the Philosopher") and Avicenna, Thomas Aquinas (1225–1274) understood the soul to be the first actuality of the living body. Consequent to this, he distinguished three orders of life: plants, which feed and grow; animals, which add sensation to the operations of plants; and humans, which add intellect to the operations of animals. Concerning the human soul, his epistemological theory required that, since the knower becomes what he knows, the soul is definitely not corporeal—if it is corporeal when it knows what some corporeal thing is, that thing would come to be within it. Therefore, the soul has an operation which does not rely on a body organ, and therefore the soul can exist without a body. Furthermore, since the rational soul of human beings is a subsistent form and not something made of matter and form, it cannot be destroyed in any natural process.
  
  The full argument for the immortality of the soul and Aquinas' elaboration of Aristotelian theory is found in Question 75 of the First Part of the Summa Theologica. Aquinas affirmed in the doctrine of the divine effusion of the soul, the particular judgement of the soul after the separation from a dead body, and the final resurrection of the flesh. He recalled two canons of the 4th-century De Ecclesiasticis Dogmatibus for which "the rational soul is not engendered by coition" (canon XIV), and "is one and the same soul in man, that both gives life to the body by being united to it, and orders itself by its own reasoning." Moreover, he believed in a unique and tripartite soul, within which are distinctively present a nutritive, a sensitive and intellectual soul. The latter is created by God and is taken solely by human beings, includes the other two types of soul and makes the sensitive soul incorruptible.