The philosophic legacy of Aristotle was to irrevocably alter the course of Western thought, contributing his knowledge and wisdom even to the advancement of biology through his dissection and proto-taxonomic classifications, as well as to human learning itself. He was also Alexander the Great's personal tutor and founded his own academy called the Lyceum.
Among his major contributions to philosophy was a critique of his own teacher, Plato's, theory of perfect or eternal "forms."
Rather than accept this notion that "true reality" lay somewhere removed from physical existence, Aristotle observed that true reality existed precisely in that physical existence that Plato rejected. He argued in favor of direct observation and experience over abstract thought and reasoning — an attitude that informed his own philosophy as well as those that followed.