Pythagoras, one of the most famous and controversial ancient Greek philosophers, lived from ca. 570 to ca. 490 BCE. He spent his early years on the island of Samos, off the coast of modern Turkey. At the age of forty, however, he emigrated to the city of Croton in southern Italy and most of his philosophical activity occurred there. Pythagoras wrote nothing, nor were there any detailed accounts of his thought written by contemporaries. By the first centuries BCE, moreover, it became fashionable to present Pythagoras in a largely unhistorical fashion as a semi-divine figure, who originated all that was true in the Greek philosophical tradition, including many of Plato's and Aristotle's mature ideas. A number of treatises were forged in the name of Pythagoras and other Pythagoreans in order to support this view. The Pythagorean question, then, is how to get behind this false glorification of Pythagoras in order to determine what the historical Pythagoras actually thought and did. In order to obtain an accurate appreciation of Pythagoras' achievement, it is important to rely on the earliest evidence before the distortions of the later tradition arose. The popular modern image of Pythagoras is that of a master mathematician and scientist. The early evidence shows, however, that, while Pythagoras was famous in his own day and even 150 years later in the time of Plato and Aristotle, it was not mathematics or science upon which his fame rested. Pythagoras was famous (1) as an expert on the fate of the soul after death, who thought that the soul was immortal and went through a series of reincarnations; (2) as an expert on religious ritual; (3) as a wonder-worker who had a thigh of gold and who could be two places at the same time; (4) as the founder of a strict way of life that emphasized dietary restrictions, religious ritual and rigorous self discipline. It remains controversial whether he also engaged in the rational cosmology that is typical of the Presocratic philosopher/scientists and whether he was in any sense a mathematician. The early evidence suggests, however, that Pythagoras presented a cosmos that was structured according to moral principles and significant numerical relationships and may have been akin to conceptions of the cosmos found in Platonic myths, such as those at the end of the Phaedo and Republic. In such a cosmos, the planets were seen as instruments of divine vengeance (“the hounds of Persephone”), the sun and moon are the isles of the blessed where we may go, if we live a good life, while thunder functioned to frighten the souls being punished in Tartarus. The heavenly bodies also appear to have moved in accordance with the mathematical ratios that govern the concordant musical intervals in order to produce a music of the heavens, which in the later tradition developed into “the harmony of the spheres.” It is doubtful that Pythagoras himself thought in terms of spheres, and the mathematics of the movements of the heavens was not worked out in detail. There is evidence that he valued relationships between numbers such as those embodied in the so-called Pythagorean theorem, though it is not likely that he proved the theorem. Pythagoras' cosmos was developed in a more scientific and mathematical direction by his successors in the Pythagorean tradition, Philolaus and Archytas. Pythagoras succeeded in promulgating a new more optimistic view of the fate of the soul after death and in founding a way of life that was attractive for its rigor and discipline and that drew to him numerous devoted followers.

Heraclitus of Ephesus (Greek: Ἡράκλειτος ὁ Ἐφέσιος,c.535 – c.475 BCE) was a pre-Socratic Greek philosopher, a native of the Greek city Ephesus, Ionia, on the coast of Asia Minor. He was of distinguished parentage. Little is known about his early life and education, but he regarded himself as self-taught and a pioneer of wisdom. From the lonely life he led, and still more from the apparently riddled and allegedly paradoxical nature of his philosophy and his stress upon the needless unconsciousness of humankind, he was called "The Obscure" and the "Weeping Philosopher". Heraclitus was famous for his insistence on ever-present change as being the fundamental essence of the universe, as stated in the famous saying, "No man ever steps in the same river twice". This position was complemented by his stark commitment to a unity of opposites in the world,stating that "the path up and down are one and the same". Through these doctrines Heraclitus characterized all existing entities by pairs of contrary properties, whereby no entity may ever occupy a single state at a single time. This, along with his cryptic utterance that "all entities come to be in accordance with this Logos" (literally, "word", "reason", or "account") has been the subject of numerous interpretations.

Protagoras (/proʊˈtæɡərəs/; Greek: Πρωταγόρας; c. 490 – c. 420 BC)[1] was a pre-Socratic Greek philosopher and is numbered as one of the sophists by Plato. In his dialogue, Protagoras, Plato credits him with having invented the role of the professional sophist. He also is believed to have created a major controversy during ancient times through his statement that, "Man is the measure of all things", interpreted by Plato to mean that there is no absolute truth, but that which individuals deem to be the truth. Although there is reason to question the extent of the interpretation of his arguments that has followed, that concept of individual relativity was revolutionary for the time, and contrasted with other philosophical doctrines that claimed the universe was based on something objective, outside of human influence or perceptions.

Gorgias (/ˈɡɔːrdʒiəs/; Greek: Γοργίας Ancient Greek: [ɡorɡíaːs]; c. 485 – c. 380 BC) was a Greek sophist, Italiote, pre-Socratic philosopher and rhetorician who was a native of Leontini in Sicily. Along with Protagoras, he forms the first generation of Sophists. Several doxographers report that he was a pupil of Empedocles, although he would only have been a few years younger. "Like other Sophists he was an itinerant, practicing in various cities and giving public exhibitions of his skill at the great pan-Hellenic centers of Olympia and Delphi, and charged fees for his instruction and performances. A special feature of his displays was to invite miscellaneous questions from the audience and give impromptu replies." He has been called "Gorgias the Nihilist" although the degree to which this epithet adequately describes his philosophy is controversial. His chief claim to recognition is that he transplanted rhetoric from his native Sicily to Attica, and contributed to the diffusion of the Attic dialect as the language of literary prose.

611 BC - 547 BC Greek philosopher and astronomer Anaximander constructed the first precise geometrical model of the universe, which, from one primordial substance, he speculated, arose out the separation of opposite qualities. He lived in Asia Minor, before Socrates. He belonged to the school and learned the teachings of Thales, his master. He succeeded Thales as the second master of that school and counted Anaximenes and arguably Pythagoras among his pupils. People today know little of his life and work. According to available historical documents, people know that he wrote down his studies despite only one extant fragment of his work. After his death, fragmentary testimonies, found in documents, provide a portrait of the man. An early proponent of science, he tried to observe and to explain different aspects with a particular interest in its origins. He claimed that laws rule nature just like human societies, and nothing disturbs its balance and lasts long, Contributions of Anaximander like many thinkers of his time relate to many disciplines. He tried to describe the mechanics of celestial bodies in relation to the Earth. In physics, his postulation of the indefinite source of all things led to a new level of conceptual abstraction. His knowledge allowed him to introduce the gnomon. He created a map that contributed greatly to the advancement of geography of the world. The politics of Miletus also involved him, and people sent him as a leader to its colony. Anaximander claimed that an "indefinite" principle gives to all natural phenomena. Carl Sagan claims that he conducted the earliest recorded scientific experiment.

"Anaximenes of Miletus (c. 585 – c. 528 BC) was an Ancient Greek Pre-Socratic philosopher active in the latter half of the 6th century BC. One of the three Milesian philosophers, he is identified as a younger friend or student of Anaximander. Anaximenes, like others in his school of thought, practiced material monism. This tendency to identify one specific underlying reality made up of a material thing is what Anaximenes is principally known for today." — Wikipedia

Thales (c. 636–c. 546 B.C.E.) Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition. According to Bertrand Russell, "Western philosophy begins with Thales." Thales attempted to explain natural phenomena without reference to mythology and was tremendously influential in this respect. Almost all of the other Pre-Socratic philosophers follow him in attempting to provide an explanation of ultimate substance, change, and the existence of the world without reference to mythology. Those philosophers were also influential, and eventually Thales' rejection of mythological explanations became an essential idea for the scientific revolution. He was also the first to define general principles and set forth hypotheses, and as a result has been dubbed the "Father of Science", though it is argued that Democritus is actually more deserving of this title. In mathematics, Thales used geometry to solve problems such as calculating the height of pyramids and the distance of ships from the shore. He is credited with the first use of deductive reasoning applied to geometry, by deriving four corollaries to Thales' Theorem. As a result, he has been hailed as the first true mathematician and is the first known individual to whom a mathematical discovery has been attributed. The first recorded Western philosopher, Thales reputedly founded the Milesian school of philosophy in Ionia, a Greek province on the Aegean coast of what is now Turkey. Although little is known about his teachings, he is said to have concerned himself with the “nature of things,” with understanding the elements and origins of the physical world. Denying the approaches used by mythology in explaining the physical world, he taught that nature is composed of one basic stuff, which he thought to be water. Not his answer but his approach was what philosophers find significant. He is believed to have introduced geometry into Greece as well as to have predicted an eclipse of the sun in 585 B.C.E. By predicting an eclipse, Thales thus contributed to the idea that the heavens are separate from the gods. Joseph McCabe calls Thales “the first freethinker in history.” Most agree that Thales' stamp on thought is the unity of substance. Bertrand Russell in Wisdom of the West wrote: "The view that all matter is one is quite a reputable scientific hypothesis. ...but it is still a handsome feat to have discovered that a substance remains the same in different states of aggregation." Russell was reflecting an established tradition as did Nietzsche in his Philosophy in the Tragic Age of the Greeks: "Greek philosophy seems to begin with an absurd notion, with the proposition that water is the primal origin and the womb of all things. Is it really necessary for us to take serious notice of this proposition? It is, and for three reasons. First, because it tells us something about the primal origin of all things; second, because it does so in language devoid of image or fable, and finally, because contained in it, if only embryonically, is the thought, "all things are one." This is not, however, deterministic materialism. Thales was attempting to explain the unity observed in the free play of the qualities. Plato’s Theaetetus tells this tale: "It seems that while Thales was engaged in studying the stars and gazing upwards he fell into a cistern; whereupon he was jeered at (they say) by a witty and attractive serving-wench from Thrace for being so eager to know what was happening in the sky that he did not see what was under his nose." Matt Cherry has observed that Thales was undeterred by the jeers of saucy serving-wenches and that several younger colleagues of Thales continued his study into the “nature of things.” Chief among these first philosophers were the Ionian Greeks Anaximander, Anaximenes, and Xenophanes. More: http://www.iep.utm.edu/thales/ http://en.wikipedia.org/

"Empedocles (c. 490 – c. 430 BC) was a Greek pre-Socratic philosopher and a citizen of Agrigentum, a Greek city in Sicily. Empedocles' philosophy is best known for being the originator of the cosmogenic theory of the four Classical elements. He also proposed powers called Love and Strife which would act as forces to bring about the mixture and separation of the elements. These physical speculations were part of a history of the universe which also dealt with the origin and development of life. Influenced by the Pythagoreans, he supported the doctrine of reincarnation. Empedocles is generally considered the last Greek philosopher to record his ideas in verse. Some of his work survives, more than in the case of any other Presocratic philosopher. Empedocles' death was mythologized by ancient writers, and has been the subject of a number of literary treatments. Empedocles is considered the last Greek philosopher to write in verse and the surviving fragments of his teaching are from two poems, Purifications and On Nature." — Wikipedia