Aristotle was a polymath and one of the most influential philosophers in history. He studied under Plato for 20 years and later founded his own school, the Lyceum. He wrote on various subjects, including logic, metaphysics, ethics, politics, biology, and physics.
Speusippus was Plato's nephew and successor as the head of the Academy. He was the first to systematize Plato's teachings and introduce the distinction between the intelligible and the sensible realms. He also developed a theory of numbers and a classification of natural kinds.
Xenocrates was a friend and colleague of Aristotle and the third scholarch of the Academy. He was known for his austere and ascetic life, and his efforts to reconcile Plato's and Pythagoras' doctrines. He wrote on various topics, such as ethics, metaphysics, psychology, and mathematics.
Arcesilaus was the founder of the Middle Academy and the first to adopt a skeptical stance in philosophy. He challenged the dogmatic claims of the Stoics and other schools, and argued that nothing can be known for certain. He advocated a mode of inquiry based on suspension of judgment and probabilistic reasoning.
Plutarch was a biographer, historian, and essayist, who was also a priest of the Delphic oracle and a magistrate in his native Chaeronea. He wrote the Parallel Lives, a collection of biographies of famous Greek and Roman figures, and the Moralia, a series of ethical and literary treatises. He was influenced by Platonism and sought to promote moral and civic education.