Human beings are mortal. Aristotle was a human being. Therefore Aristotle was mortal.
The rules for this kind of reasoning were first described by the Greek philosopher Aristotle more than two thousand years ago, and they still remain an invaluable basis for logical thinking.
Aristotle was not only a logician, but also a philosopher, psychologist, moralist, political thinker and biologist.
He was the son of a doctor and for 20 years a disciple of Plato. He spent seven years in Macedonia teaching prince Alexander (soon to be Alexander the Great) then returned to Athens when Alexander took the throne.
In Athens he set up a school nicknamed the Peripatetic ("walking about") School because students walked around the gardens while listening to the teacher. This nickname suited his philosophy, which emphasized change. Nature, Aristotle said, aims at a particular end. Oak seeds, for example, have an internal principle that makes them try to grow into oak trees.
His ethical teachings are contained in "Nicomachean Ethics" (335 to 322 BC), one of the world's great books. It teaches people to aim at the "mean." The mean is a point between two extremes. For example, courage is midway between cowardice and foolhardiness.
Aristotle also wrote about plants and animals and astronomy. Many of his ideas in these areas have been discarded today. For example, his notion that the earth is the center of the universe was proven wrong by Copernicus and Galileo.
Aristotle's works came to Europe by a roundabout way. Though lost in the West, his works had been preserved in Syria. When the Muslim Arabs conquered Syria, they found Aristotle's works and took them to Spain after conquering it.
From there Aristotle became known throughout Europe. Medieval scholars -- particularly the Jewish philosopher Maimonides and Christian theologian Thomas Aquinas -- used Aristotle's ideas in defense of their religions.
