Thus the soul resembles the hand. The hand is the most perfect of organs, for it takes the place in man of all the organs given to other animals for purposes of defense or attack or covering. Man can provide all these needs for himself with his hands. And in the same way, the soul in man takes the place of all the forms of being, so that through his soul a man is, in a way, all being or everything; his soul being able to assimilate all the forms of being–the intellect intelligible forms and the senses sensible forms.
Thomas Aquinas, Commentary on the De Anima, Book II, Lectio 13