Theophrastus c. 371 BC – c. 287 BC

Theophrastus of Eresus was an ancient Greek philosopher and the immediate successor of Aristotle as head of the Peripatetic School at the Lyceum in Athens. He directed the school for thirty-five years, from 322 BC until his death, and developed Aristotle's research programme particularly in botany, where his Enquiry into Plants and On the Causes of Plants founded systematic plant science. His Characters, a series of brief literary sketches of moral types, has been a model for the genre from antiquity to the present. His extensive philosophical writings on metaphysics, logic, and ethics survive only in fragments. He is reported to have brought the Peripatetic school to its peak, with two thousand students attending his lectures.

Theophrastus was born around 371 BC in Eresus on the island of Lesbos. He came to Athens as a young man, studied first with Plato and then with Aristotle, with whom he formed a close intellectual partnership during the years of the Lyceum. When Aristotle withdrew from Athens in 322 BC, he left the school and his library to Theophrastus, who directed the Peripatos for the next thirty-five years.

Under his leadership the Lyceum reached its largest enrollment, reportedly some two thousand students, and produced a vast body of research. The surviving works include the Characters — thirty vivid sketches of moral types — the Enquiry into Plants and On the Causes of Plants, on which all later botany was built, the Metaphysics fragment, and treatises on stones, fire, weather signs, and sense perception.

Theophrastus refined and in places revised Aristotle's logic, physics, and ethics, defended the contemplative life against Stoic and Cynic challenges, and is generally regarded as the founder of botany as a systematic science. He died in Athens around 287 BC at an advanced age, and his will, preserved by Diogenes Laertius, made provision for the continuation of the school and its garden.