Soul

===Thomas Aquinas===
Following Aristotle (whom he referred to as "the Philosopher") and Avicenna, [[Thomas Aquinas]] (1225–74) 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.<ref>{{cite web|last=Aquinas|first=Thomas|title=Quaestiones Disputatae de Veritate|url=http://www.corpusthomisticum.org/qdv02.html#51826|language=la|access-date=2016-02-23|url-status=live|archive-url=https://web.archive.org/web/20160304023626/http://www.corpusthomisticum.org/qdv02.html#51826|archive-date=4 March 2016}}</ref> 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.<ref>{{cite web|last=Aquinas|first=Thomas|title=Super Boetium De Trinitate|url=http://www.corpusthomisticum.org/cbt.html#84681|language=la|access-date=2016-02-23|url-status=live|archive-url=https://web.archive.org/web/20160304110654/http://www.corpusthomisticum.org/cbt.html#84681|archive-date=4 March 2016}}</ref> 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 ''[[Gennadius of Massilia#De Ecclesiasticis Dogmatibus|De Ecclesiasticis Dogmatibus]]'' for which "the rational soul is not engendered by coition" (canon XIV)<ref>Cited in {{cite web|url=https://www.newadvent.org/summa/1118.htm#article2|title=Summa Th. 1:118:2, Objection 4}}</ref> 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."<ref>{{cite book|url=https://www.newadvent.org/summa/1076.htm#article2|title=Summa Theologiae of St Thomas Aquinas - Pars I - Quaestio 76 - Article 3. Whether besides the intellectual soul there are in man other souls essentially different from one another?|translator-last1=Fathers of the English Dominican Province|year=1920}} Full citation of the canon: ''Nor do we say that there are two souls in one man, as James and other Syrians write; one, animal, by which the body is animated, and which is mingled with the blood; the other, spiritual, which obeys the reason; but we say that it 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.''</ref> 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.<ref>''Summa th. '', Pars I, Quaestion 76, Article 3, Reply to Objection 1.</ref>