1 1. The Presocratics This book is an introduction to the turning point in the history of human thought that began in ancient Greece over twenty-five hundred years ago. Starting with the discovery of the concept of nature (physis), and then the ethical philosophy of Socrates and his followers, human beings began to reflect critically about themselves and the universe in which they lived. The first philosophers of Western history were the Presocratics, so named by later historians because they came before the pivotal figure of ancient philosophy, Socrates. The great achievement of the Presocratics was to discover the philosophical ideas of nature and science, and to begin to articulate a scientific understanding of the universe. The leading Presocratic philosophers were the Milesians, the Pythagoreans, Heraclitus, Parmenides and Zeno, Empedocles and Anaxagoras, and the Atomists. The Milesians: Science and Nature Roughly speaking we can say that before the Milesians, the ancient Greeks experienced the world as filled with gods and divine spirits who were closely identified with parts or aspects of both nature and culture. Zeus was manifest in the sky and lightning, justice and law, Poseidon in the storms and the sea, Aphrodite in sexual passion, Iris in the rainbow, Demeter in the ever- returning grain, Hera in childbirth, feminine wisdom, Apollo in religious purity and self-restraint, Dionysus in wine and ecstasy, etc. There were river gods and spirits of sacred groves, there were earth-deities, there were presences and powers filling an enchanted universe. After the Milesians, educated Greeks and Romans began to think of nature (physis) as a realm with laws of its own, distinct from the gods, and of knowledge and truth as deriving from observation and reasoning, rather than ancestral tradition and law. This was the beginning of science and of a scientific, secular conception of nature and knowledge. The objective world of natural science (logos) replaced what came to be seen as a subjective world of religious imagination (mythos). 2 There are two ways in which intellectual historians have described the Milesian discovery. The first involves a new idea of how to acquire knowledge of the world. The Milesians were also the first methodological naturalists, the first to insist that scientific knowledge of the world must be acquired by observation and reasoning (as opposed to the hearsay of myths, traditions, sacred books, seers, dreams and voices sent by the gods). Whereas the Greek religious tradition based its claim to truth (revelation) on faith in ancestral authority and the claim of divine inspiration, the Greek scientific tradition based its claim to truth on evidence gained from sense-experience (empeiria). (Later, the theory that all knowledge was acquired this way was called empiricism.) The scientific method relies on the sensory world for its facts and on human reason to organize, interpret and explain those facts in terms of general laws. This is what gives science its objective character, what allows scientists from China or India or the US all to engage in science together, and not fall into methodological conflicts, even if they disagree wildly about art, morality, politics or religion. By contrast, people of different religions have different foundations for belief—their sacred authorities assert non-naturalistic ways of founding truth, their Gods command different laws and truths and practices. This is part of the reason why religious disputes can seldom be decided by rational means. They are not open to a common, objective method of testing and thereby falsifying or verifying the truth-claims of the opposing religious beliefs. The idea of methodological naturalism includes a new conception of truth (based on proof) vs. that of revelation (based on sacred authority). The other aspect of the Milesian discovery invokes a new conception of reality. In this respect, the Milesians were the first metaphysical naturalists, i.e. the first thinkers to claim that everything that exists derives from a common ground of natural substance, that the world is one material whole—the earth, the sky, the water, the air, fire, plants, animals, stars, humans, clouds, artifacts, everything. We can understand how this idea might arise in a society in which various types of technical knowledge were well advanced, and there was travel and trade between people of different cultures. The Greeks who built strong sea-faring ships, studied the movements of the stars at night, learned the material principles that allowed them to construct large buildings, dissected the human body and discovered medications for disease—they might well begin to wonder if “Zeus” really was present in lightning, “Poseidon” in the storm at sea, or “Apollo” in disease. As they intermingled with Egyptians and Babylonians and Scythes whose gods and customs were very different from their own, a new thought began to dawn: the idea of nature. QUESTION: You cannot be a scientist unless you embrace methodological naturalism, but what about metaphysical naturalism? Does a scientist have to be a metaphysical naturalist? 3 How did Milesian natural science and philosophy develop? Thales of Miletus We have just four quotes from Thales: 1. All things are water (hydor). 2. The earth rests on water. 3. All things are full of gods. 4. The magnet has a soul. These statements seem inconsistent with the naturalistic viewpoint I have been attributing to the Milesians. But if read in contrast to the world of the Greek polytheistic religion, they take on a naturalistic meaning. Thus the Greek word hydor probably meant not water as we understand it, but something more like “flowing liquid matter,” the fluid source or nutrient glue of the living, self-moving natural world. This implies that Thales conceived of “all things” as one unified and animated whole—as a biosphere nurtured by water (cosmology); as originating in water (cosmogony); or as made out of water (constituent analysis). This is the idea of one natural universe—the idea I have called metaphysical naturalism. Thales’ bottom-up conception of the structure of the natural world, which he bequeathed to his successors, had this form: Laws of nature governing / \ Changing physical world (ta panta, “all things”) / \ originating out of / \ Being, the unchanging (arche, “source” or “principle” = hydor) Since everything arises from or is composed out of the underlying material substance (Thales’ hydor, i.e. “flowing liquid matter”, Anaximander’s apeiron for 4 “the indefinite,” Anaximenes aer for “air” or “space”), there are no non- corporeal beings, i.e. no gods or immortal souls or anything of that kind. Thales’ other quotes also fit this scientific vision. “The earth rests on water” suggests there is a natural explanation of the earth’s place in the universe, in contrast to the myth of it resting on the shoulders of Atlas. Even the statements that “all things are full of gods” and “the magnet has a soul” can be interpreted naturalistically—“soul” (psyche) now simply meaning a natural animating or self-moving principle in matter, gods (theoi) now pointing to ever- recurrent natural laws and powers. These interpretations are consistent with the direction Thales’ students took in developing his naturalistic vision, beginning with Anaximander. Anaximander Anaximander (610-546 BC) is credited with being the first person to make a map of the entire earth; to study human embryos; and to conceive of the universe as spherical in shape. We have a fairly large body of fragments from him, which reveal a far-ranging scientific mind. Here are some of the statements attributed to Anaximander: 1. The first principle and origin of being is neither water nor any of the other things called elements, but some other nature which is unlimited (a-peiron), out of which come to be all the heavens and the things in them. 2. What arose from the eternal [the apeiron] and is productive of hot and cold was separated off at the coming-into-being of this cosmos, and a kind of sphere of flame from this grew around the dark mist about the earth like a bark about a tree. When it was broken off and enclosed in circles, the sun, moon, and stars came to be. 3. The first animals were produced in moisture. When these water-creatures came out onto the land, their protective covers broke off, and they lived a different sort of life. The first humans arose from fish or fish-like creatures. 4. The earth is round and cylindrical, three times as long as in diameter. The circle of the sun is 27 times that of the earth, the moon 18 times that of the sun. 5. The things that are perish into the things out of which they come to be, according to necessity, for they pay penalty and retribution to each other for their injustice in accordance to the ordering of time. What is the significance of these quotations? The first quote suggests that Anaximander, like Thales, may have conflated the ideas of metaphysical and methodological materialism. In any case, for the Milesians scientific knowledge of nature begins with the principle that there is an underlying physical substance to all things, which Anaximander 5 conceives of as indeterminate (implied by the transformation into one another of elementary bodies such as earth, air, fire and water). It is also interesting that Anaximander’s idea of the Apeiron (Un-limited or Bound-less) seems to have arisen from criticism of Thales’ view of hydor, a determinate form of matter, as the underlying reality. This suggests that Thales encouraged his students to develop their own theories, rather than submit to his. Greek science was from the beginning an evidence-driven and self-critical communal enterprise, rather than one based on authority and dogma.