Thales held that all is water. Anaximenes took the view that there is nothing but air. Pythagoras contended that reality is made of numbers. Parmenides averred that all is one and nothing changes. Heraclitus insisted that everything is in flux, and you cannot step into the same river twice. Zeno offered proofs that nothing moves. Anaxagoras was of the opinion that everything contains a little bit of hair.
They seem to have had some pretty wacky ideas, those ancient Greeks, the founders of Western thought. Did they just say whatever came into their heads? One of the great merits of Anthony Gottlieb's "The Dream of Reason," a survey of Western philosophy from the ancient Greeks to the Renaissance, is that it explains just why they held these apparently strange views and why they are, by no means, as silly as they may sound to modern ears. The book invites comparison with Bertrand Russell's monumental "History of Western Philosophy," which was a bestseller when it came out in 1945, but Gottlieb's book is less idiosyncratic and based on more recent scholarship. Perhaps it is too much to expect that in these days it might also become a bestseller, but it is certainly a book in the finest tradition of responsible popularization. Thales would be proud.
Thales and the rest are the so-called Presocratics, who flourished in the 6th century BC, some 200 years before Socrates came along. As Gottlieb reminds us, their signal achievement was to replace religious pseudo-explanations ('It happens that way because that's how the gods intend it') with attempts at naturalistic explanation in terms of constituents and causes. Thus Thales observed that water can take solid, liquid and gaseous forms, that it was essential to life, that it afforded a simple explanation of natural phenomena-a wrong explanation, yes, but still a lot better than invoking the gods and magic of his forebears. Anaximenes noted the connection between air and the preservation of soul (you die if you stop breathing), and he had the idea that air might be compressed into substances of different types: wind, clouds, maybe Earth. Nature, he suspected, was a series of variations on a central theme. Pythagoras was impressed with the way nature is mathematically describable, especially in terms of geometry, so he allowed himself a touch of hyperbole. Parmenides argued that we cannot talk about what is not, so given that change is defined by some people in terms of negation-the house, for example, was not that color before and now it is-then change is not possible, nor is the idea of one thing not being another.
A funny argument, to be sure, but a real argument nonetheless, an attempt to reason logically about the world. Heraclitus, contrarily, was struck by the incessant changes in nature, even in the most permanent of things, noting that a river is really a succession of changing bodies of water. Zeno ingeniously argued that you cannot travel any distance until you first travel part of that distance, and that is true no matter how small the distance is; hence you cannot get started. Thus it is that Achilles must forever lag behind the tortoise in his famous paradox. And good old Anaxagoras was mightily impressed by the fact that hair grows out of your head even though there is no hairy stuff inside it, or in the food you eat that eventually leads to hair. How can hair come from non-hair? Answer: There is a microscopic amount of hair in every cell of your body, and indeed in the food you eat. Generalizing, every substance must contain a bit of every other substance, in order to explain how substances get transformed into other substances. This is an extravagant theory, no doubt, but it is a theory designed to solve a real explanatory problem. It is not just a wild assertion.
In all of these cases Gottlieb brings out the logic behind the apparent eccentricity. He shows that one of the pre-Socratics' central insights was that the variety of the world might mask an underlying unity or simplicity. This reached its zenith in the remarkable suggestion, by Democritus (about 460-370 BC), that nature consists of "atoms in the void," imperceptibly small particles of different shapes suspended in empty space, that join together to form the observable world. This seems to have been a pure hunch on the part of Democritus, but it forms the basis of the modern view of things, and it was not until the Renaissance that the idea received substantial support.