Socratic philosophy

Philosophy in classical Greece is the ultimate origin of the western conception of the nature of a thing. The philosophical study of human nature itself originated, according to Aristotle at least, with Socrates, who turned philosophy from study of the heavens to study of the human things. Socrates is said to have studied the question of how a person should best live, but he left no written works. It is clear from the works of his students Plato and Xenophon, and also what was said by Aristotle (Plato's student) about him, that Socrates was a rationalist and believed that the best life and the life most suited to human nature involved reasoning. The Socratic school was the dominant surviving influence in philosophical discussion in the Middle Ages, amongst Islamic, Christian, and Jewish philosophers.

The human soul in the works of Plato and Aristotle has a divided nature, divided in a specifically human way. One part is specifically human and rational, and divided into a part which is rational on its own, and a spirited part which can understand reason. Other parts of the soul are home to desires or passions similar to those found in animals. In both Aristotle and Plato spiritedness, thumos, is distinguished from the other passions or epithumiai. The proper function of the "rational" was to rule the other parts of the soul, helped by spiritedness. By this account, using one's reason is the best way to live, and philosophers are the highest types of humans.

Aristotle, Plato's most famous student, made some of the most famous and influential statements about human nature. In his works, apart from using a similar scheme of a divided human soul, some clear statements about human nature are made:
Man is a conjugal animal, meaning an animal which is born to couple when an adult, thus building a household (oikos) and in more successful cases, a clan or small village still run upon patriarchal lines.
Man is a political animal, meaning an animal with an innate propensity to develop more complex communities the size of a city or town, with a division of labor and law-making. This type of community is different in kind from a large family, and requires the special use of human reason.
Man is a mimetic animal. Man loves to use his imagination (and not only to make laws and run town councils). He says "we enjoy looking at accurate likenesses of things which are themselves painful to see, obscene beasts, for instance, and corpses." And the "reason why we enjoy seeing likenesses is that, as we look, we learn and infer what each is, for instance, 'that is so and so.'"

For Aristotle, reason is not only what is most special about humanity compared to other animals, but it is also what we were meant to achieve at our best. Much of Aristotle's description of human nature is still influential today, but the particular teleological idea that humans are "meant" or intended to be something, has become much less popular in modern times.

For the Socratics, human nature, and all natures, are metaphysical concepts. Aristotle developed the standard presentation of this approach with his theory of four causes. Human nature is an example of a formal cause according to Aristotle. Their teleological concept of nature is associated with humans having a divine component in their psyches, which is most properly exercised in the lifestyle of the philosopher, which is thereby also the happiest and least painful life.