In this illustrated lecture, I will outline the major contributions of the ancient Greek philosopher Aristotle (384-322 BCE) to human thought.

Aristotle was first and foremost a biologist who got his hands dirty examining marine specimens off the coast of the island of Lesbos in the eastern Aegean Sea. He is also ranked among the five greatest logicians in human history, on the basis of his invention of a system for reasoning about relations between non-empty classes of things (a system that contemporary logicians have proved is sound and complete) as well as of his method of �contrasted instances� for showing that a conclusion does not follow necessarily from the reasons offered in its support. He worked out a theory of mathematical and scientific proof whose basic outlines still hold good today. He introduced an abstract vocabulary for talking about things in general that we inherit today in our talk of species and genera, elements and compounds, matter and form, substances and their properties, and essential and accidental characteristics.

He distinguished different senses of the word �why� in the form of a theory of kinds of causes. He defended a purposive understanding of natural phenomena in terms for example of the functions that the organs in an animal or a plant serve�an understanding that can in fact be harmonized with the contemporary theory of evolution of biological species developed from Darwin�s ideas.

He articulated in a very clear way a rigorously philosophical conception of God as the �first unmoved mover� of everything in the universe. He was the first theorist about life, perception and thinking to reject the idea that these capacities reside in a �thing� (e.g. a �vital force� or soul or mind) distinct from the complex of physical organs that make up an organism with those capacities. He introduced into biology the idea of homologous organs (for example, the roots of a plant being like the mouth of an animal). He developed an influential analysis of good character traits like courage and moderation as lying in a mean between a vice of excess and a vice of deficiency.

His wise and influential writing on forms of government reflects his study of the constitutional histories of 156 different states, histories prepared under his direction. His treatise on the art of public speaking still informs contemporary theorizing about, and practice of, speech communication. His notion of a good tragedy as one in which an otherwise fine person is brought down by a tragic flaw still influences playwrights and theatre-goers today.

And there is more.