Early Greek philosophers
Philosophy, more or less, begins with Thales. As tradition holds, Thales is the first so-called Greek philosopher. However, this is based only on historical recording. He could have, after all, been reflecting on a longer tradition that preceded him. Record has it that the early philosophers regularly frequented Egypt and the Near East which undoubtedly suggests that there may be validity to the notion that Thales—and others—borrowed many ideas from cultures and traditions older than themselves. One thing is for sure, the Ionian tradition that Thales and his pupil Anaximander founded made a decisive and deliberate break from “cosmologies based on divine genealogies and anthropomorphic gods,” in direct contrast to Hesiod’s Theogony and Pherecydes’ Theology (James Warren, Presocratics, p. 24). The project of early Greek philosophy centered around the search for the arkhe (source, beginning, origin) of all things. In other words, “the most fundamental and everlasting matter out of which all things are composed and into which they all eventually decay” (p. 25). This investigation proceeded by physical and metaphysical enquiry.
Since we do not have any primary sources on Thales we must rely upon other philosophers, namely Artistotle, who recorded and interpreted the thoughts of early thinkers. According to Artistotle, Thales believe all matter originated from water; or at least all matter is some form of water. Thales postulated, furthermore, that the earth floated on water which explained the cause of earthquakes. Perhaps, even, he considered all objects—including inanimate ones—to possess souls in order to account for change and motion. He was interested, most of all, in explaining natural phenomena; a problem most ancient Greek philosophers shared.
Anaximander followed Thales in also giving a natural and philosophical account of the universe. His arkhe or source, however, was boundless (apeiron). As such, his ontological position was polemically against Thales. Given the boundlessness of the world Anaximander conjectured that the cosmos could never be exhausted and allowed the generation of innumerable worlds. Furthermore, the boundless figure of Anaxminader’s cosmology was eternal as well as the source and mover of all elements—much like any description of traditional gods, ironically. “The apeiron is an attempt to explain the observed variety and change in the world by offering a single ultimate source and cause of all the different and opposed elements in the world” (p. 31). Anaximander also recognized a “scientific” worldview and is attributed the bearer of the principle of sufficient reason. In brief, Anaximander held that if one argument was reasonably sound, it proved nothing if the opposite proposition possessed just as much supportive evidence. One position, therefore, must be more reasonable than another for it to be considered legitimate. Given this brief description, we can see why Anaximander was led to confidently speculate that there was some reason and explanation for the ways of the world. Hence, he recognized a world that was predictable in is some sense.
Anaximenes continued in the footsteps of the Ionian tradition by enquiring into the “single stuff” that underlies the origin of all things. His novel contribution, however, was to replace arche with aer (air) as the substance that underlies other substances. Furthermore, Anaximenes explained the plurality of existence based upon a sliding scale of density (e.g., the more rare air was it gradual became fire whereas the more condensed air became it transformed into wind). By this explanation Anaximenes showed that all things were unified. But, in order to account for the difference between animate and inanimate things, Anaximenes posited that it was breath (pneuma) or soul (psyche) that animated air (aer). Although, according to critics of Anaximenes, the two poles tend to be conflated and “closely assimilated” in his thought.
Pythagoras wrote nothing himself but was the first to be called a “philosopher” in his time. He is, of course, famous for his discoveries in mathematics—specifically in arithmetic and geometry—but “[t]he long-lived Pythagorean tradition has obscured much of the original nature of his teachings and sources throughout antiquity are too eager to ascribe various later philosophical and mathematical theories directly to Pythagoras” (p. 37). From what we know of Pythagoras, he believed in the immortality of the soul, reincarnation—or metempsychosis, that nothing is new per se but everything recurs, and that all ensouled creatures are akin. It is also known that upon emigrating to Italy around 530 BC he founded a secret and moral society that was famously vegetarian (given the possibility that one might accidentally eat a reincarnated acquaintance).