Aristotle (384-323 BC) was born in Macedonia (northern Greece). He learned medicine from his father and philosophy from Plato. He wrote the constitution of Athens, served as counselor to Hermias, tutored Alexander the Great, and is sometimes called the first psychologist..
Aristotle proposed a tri-level hierarchy of faculties: nutrition, perception and intellect. Nutrition applies to all living things, perception to all animals, and intellect to all people. Intellect is like a sixth sense, a “common sense,” that synthesizes input from the five perceptual senses. In his book On The Soul, he proposes that the general distinction of form and matter also describes what makes us human. The soul (psyche) and the body are aspects of the same entity; they are the form and matter (respectively) of human existence.
For Aristotle, form is active and life itself is active. The psyche is the active part of intellect; consequently, psychology is the study of the principle of life, how a person acts intellectually and morally. According to Aristotle, thinking and knowing are different. Thinking uses images but knowing is more like active intuition. So intellect is not a collection of facts but the capacity to find knowledge.
Language is distinctively human, the product of a rational animal. Man alone has language because man alone has the ability to reason. By man, Aristotle meant males from the upper class of society, not women or non-Greeks. By reasoning, he meant the ability to tell right from wrong. Right is not based on moral absolutes but by balancing opposite poles. By this reasoning, courage is not a separate virtue; it’s the midpoint between rashness and cowardice.
Although the Greek culture was polytheistic, Aristotle argued for the existence of a divine principle above all the rest. Since the world had always existed, God was not thought of as a creator but as the Prime Mover (first cause) of the chain of events we call history. For Aristotle, God was pure intellect; perfect unity and unchangeable but not personal or interested in our lives.
Aristotle didn’t coin the term “logic” but he defined it and founded it as a science. Indeed, into the 20th century, all logic was Aristotelian logic. His syllogisms were chains of reasoning that began with a proposition and ended with a conclusion. This proposition-proposition-conclusion format tests the logical consistency of ideas and the validity of logic. Building on Plato’s deductive method, Aristotle’s analytic approach was both inductive and deductive. Plato believed that the world we perceive is but an imperfect copy of the real world. Aristotle held that the world perceived is the real world and there is no need to assume perceptions are imperfect copies of a separate world of ideas. Consequently, careful observation of the world perceived can lead to principles which can be applied to specific circumstances.
Ironically, it is careful observations that showed the errors of Aristotle’s scientific conclusions. Like Hippocrates, Aristotle noted four basic elements, each with its own “specific gravity.” But in addition to earth, air, fire and water, Aristotle added a fifth: ether (to describe the content of the heavens). Similarly, his geocentric cosmology, his fixed species model of zoology and his assumptions about falling objects were all overturned by careful observations and the application of Aristotelian logic.
But consider how enduring his idea were. Aristotle’s belief that heavier objects fall faster than lighter ones lasted until Galileo dropped weights from the Leaning Tower of Pisa. With minor exceptions, Aristotle’s view that earth is the center of the universe went unchallenged until Capernicus. And is wasn’t until Charles Darwi’s careful observations that evolution replaced the belief in a fixed set of species. As for ether being a fundamental element of physics, it was completely discounted until Albert Einstien’s 1905 special theory of relativity. And in psychology, Aristotle’s 3 laws of association (i.e., similarity, contiguity, and opposites) are still thought to impact encoding processes.
As a Macedonian, not an Athenian, Aristotle had to deal with the stigma of being an outsider (from a different city-state). Perhaps this is why he was not selected to succeed Plato (the job went Plato’s nephew). In any case, he left Athens after the death of Plato. About the same time, Aristotle married (at age 38). He had a daughter by his first wife, remarried after her death and had a son by his second wife. He was 42 when he began tutoring 13 year old Alexander the Great. And 50 when he returned to Athens opened his school. Officially Aristotle’s school was named the Lyceum but informally it was called the “walking school.” His students learned by strolling around the grounds with their teacher and became known as peripatetics. After death of Alexander, anti-Macedonian sentiment again arose in Athens and Aristotle moved to his mother’s estate on the island of Euboea, where he died the following year.
For more on the subject, check out this video on Hippocrates, Democritus and Aristotle.