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Period: 624 BCE to 546 BCE
Thales of Miletus
Thales was the founder of the philosophy that all of Nature had developed from one source. According to Heraclitus Homericus (540–480 BCE), Thales drew this conclusion from the observation that most things turn into air, slime, and earth. Thales thus proposed that things change from one form to another. -
Period: 610 BCE to 546 BCE
Anaximander
Anaximander postulated eternal motion, along with the apeiron, as the originating cause of the world. This (probably rotary) motion caused opposites, such as hot and cold, to be separated from one another as the world came into being. -
Period: 585 BCE to 525 BCE
Anaximenes
Anaximenes is best known for his doctrine that air is the source of all things. In this way, he differed with his predecessors like Thales, who held that water is the source of all things, and Anaximander, who thought that all things came from an unspecified boundless stuff. -
Period: 579 BCE to 490 BCE
Pythagoras of Samos
Pythagoras of Samos was an ancient Ionian Greek philosopher and the eponymous founder of Pythagoreanism. The Pythagorean moral philosophy is related to Orphic mysticism. It is difficult to distinguish which elements can be ascribed to the Orphics and which to the Pythagoreans. Central to this ethical philosophy was the concept of metempsychosis; the transmigration of the soul. -
Period: 428 BCE to 348 BCE
Plato
In metaphysics Plato envisioned a systematic, rational treatment of the forms and their interrelations, starting with the most fundamental among them (the Good, or the One); in ethics and moral psychology he developed the view that the good life requires not just a certain kind of knowledge (as Socrates had suggested) -
Period: 384 BCE to 322 BCE
Aristotle
Aristotle was one of the greatest philosophers who ever lived and the first genuine scientist in history. He made pioneering contributions to all fields of philosophy and science, he invented the field of formal logic, and he identified the various scientific disciplines and explored their relationships to each other. -
Period: 341 BCE to 270 BCE
Epicurus
For Epicurus, the purpose of philosophy was to help people attain a happy (eudaimonic), tranquil life characterized by ataraxia (peace and freedom from fear) and aponia (the absence of pain). He advocated that people were best able to pursue philosophy by living a self-sufficient life surrounded by friends -
Period: 334 BCE to 262 BCE
Zeno of Citium
Zeno of Citium was the founder of the Stoic School of philosophy in Athens which taught that the Logos (Universal Reason) was the greatest good in life and living in accordance with reason was the purpose of human life. -
Period: 354 to 430
St. Augustine of Hippo
Augustine believes reason to be a uniquely human cognitive capacity that comprehends deductive truths and logical necessity. Additionally, Augustine adopts a subjective view of time and says that time is nothing in reality but exists only in the human mind's apprehension of reality. -
Period: 1225 to 1274
St. Thomas Aquinas
Aquinas believes that we should always follow our conscience, even when it is wrong or causes great harm. Since we have no way of knowing whether our consciences are wrong, they are the best guide we have as to what is the moral thing to do. -
Period: to
Immanuel Kant
His moral philosophy is a philosophy of freedom. Without human freedom, thought Kant, moral appraisal and moral responsibility would be impossible. Kant believes that if a person could not act otherwise, then his or her act can have no moral worth. -
Period: to
John Rawls
Rawls's theory of "justice as fairness" recommends equal basic liberties, equality of opportunity, and facilitating the maximum benefit to the least advantaged members of society in any case where inequalities may occur. -
Jürgen Habermas
Jürgen Habermas seeks to defend the Enlightenment and with it an “emphatical”, “uncurtailed” conception of reason against the post-modern critique of reason on the one hand, and against so-called scientism (which would include critical rationalism and the greater part of analytical philosophy) on the other.