Aristotle claims that the soul is the form and essence of all living things. The soul is composed of many parts. All living things – plants and animals – possess a soul with a generative part, which is responsible for the nutrition and reproduction of living beings. Only animals possess a soul with a sensitive part, which enable the animal to feel pleasure and pain. Some animals possess other senses such as sight, smell, and taste. Finally, only man possess a soul with the ability to think.
According to Aristotle, thinking is different from the act of sense-perception and imagination. The senses are never false, and imagination is merely the recall of past sensations. Thinking, on the other hand, can be false. Aristotle argues that thinking is composed of two operations – on passive and one active. Passive thinking is the ability of man to store abstract ideas such as man, triangle, and horse. Active thinking is the ability of man to retrieve these abstract ideas and contemplate them.
Finally, Aristotle asserts that the thinking part of the soul is immortal because it operates independent of any bodily organ; and therefore it is immaterial and incorruptible. This argument is strange to modern readers because we often ascribe thinking to the brain, but modern cognitive science still cannot account for some aspects of consciousness, which means Aristotle’s argument is not entirely refuted.
“Nature never makes anything without a purpose and never leaves out what is necessary.”
“While mind bids us hold back because of what is future, desire is influenced by what is just at hand: a pleasant object which is just at hand presents itself as both pleasant and good, without condition in either case, because of want of foresight into what is farther away in time.”
“What has been born must grow, reach maturity, and decay.”