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The founder of the philosophy that all of Nature had developed from one source. Thales observed that water was important in everyday life. Most things were moist. Life needed water for nourishment, and many things lived near water. Thales believed that water was the origin of all things in Nature. -
He is known as the "father of numbers" or as the first pure mathematician, and is best known for his Pythagorean Theorem on the relation between the sides of a right triangle, the concept of square numbers and square roots, and the discovery of the golden ratio. -
Remembered for his teaching methods and for asking thought-provoking questions. Instead of lecturing his students, he asked them difficult questions in order to challenge their underlying assumptions, a method still used in modern-day law schools. Because Socrates wrote little about his life or work, much of what we know comes from his student Plato. -
He sought to build a foundation of ideas that would serve as a guiding principle toward a happier, more thoughtful way of life. Antisthenes believed that happiness was dependent on moral virtue and that virtue could be instilled through teaching. He is Socrates' pupil. Before becoming an enthusiastic disciple of Socrates, Antisthenes studied rhetoric under Gorgias. Socrates' views on ethics were taken and refined by him, and he advocated for a life of asceticism based on virtue. -
Was an Athenian military leader, philosopher, and historian. At the age of 30, Xenophon was elected commander of one of the biggest Greek mercenary armies of the Achaemenid Empire. He emphasized the importance of self-control, which comprises one of the cardinal virtues of Greek popular morality. This is highlighted by Xenophon in many ways. Socrates is often said by Xenophon to have exemplified it in the very highest degree. -
Studied ethics, virtue, justice, and other ideas relating to human behavior. Following in Socrates’ footsteps, he became a teacher and inspired the work of the next great Greek philosopher, Aristotle. -
Was a Greek Cynic philosopher best known for holding a lantern (or candle) to the faces of the citizens of Athens claiming he was searching for an honest man. He rejected the concept of "manners" as a lie and advocated complete truthfulness at all times and under any circumstance. -
Xenocrates is known to have written a book On Numbers, and a Theory of Numbers, besides books on geometry. Plutarch writes that Xenocrates once attempted to find the total number of syllables that could be made from the letters of the alphabet. -
While also interested in ethics, studied different sciences like physics, biology, and astronomy. He is often credited with developing the study of logic, as well as the foundation for modern-day zoology. -
Regarded as the founder of ancient Skepticism. He identified as wise men those who suspend judgment (practice epochē) and take no part in the controversy regarding the possibility of certain knowledge. He proposed the neutral position of accepting things as they appear without further analysis. -
He was the founder ancient Greek philosophical school of Epicureanism, whose main goal was to attain a happy, tranquil life, characterized by the absence of pain and fear, through the cultivation of friendship, freedom and an analyzed life. His metaphysics was generally materialistic, his Epistemology was empiricist, and his Ethics was hedonistic. Epicurus also thought skepticism was untenable, and that we could gain knowledge of the world relying upon the senses. -
Hellenistic thinker who founded the Stoic school of philosophy, which influenced the development of philosophical and ethical thought in Hellenistic and Roman times. Zeno taught that tranquility can best be reached through indifference to pleasure and pain. He was also a utopian anarchist, arguing that a society of rational men and women had no need of money, courts of law, or organized institutions.