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workings of the world on pure whim (as they do, for instance, in prescientific thinking—if the gods can intervene to change the course of the stars or the boiling point of water at random, for instance, then nothing is predictable). The next task is to isolate cause and effect, the forces that cause things to happen in a predictable way. One finds an excellent example of this process in the
Histories
of Herodotus (probably written in the 430s B.C.). Herodotus starts his famous survey of Egypt (book 2) with speculation on the causes of the annual Nile floods. He considers three explanations which, he tells us, others have put forward. One is that the summer winds force back the natural flow of the water, and as they die down a larger volume of water is released in compensation. This cannot be true, he notes, because the floods occur even in years when the winds do not blow. Moreover, no other rivers show this phenomenon. The second explanation is that the Nile flows from an ocean that surrounds the earth. This is not a rational explanation, says Herodotus; it can only be legend. Probably Homer or some other poet (he says somewhat scornfully) introduced the idea. The third explanation is that it is melting snows that cause the floods, but surely, says Herodotus, the further south you go the hotter it gets, as the black skins of the “natives” suggest. Snow would never fall in such regions. He goes on to provide an elaborate explanation of his own, based on the sun causing the Nile to evaporate just at a time when rainfall is low, so creating an artificially low volume of water in comparison to which the normal flow is a “flood.” He misses the true cause, the heavy summer rains that run down from the mountains of Ethiopia, but even if he reaches the wrong answer, Herodotus is aware of and consciously rejects mythological explanations. He uses observation and reason to discard some explanations and formulate others. Here is the process of “scientific” thinking at work. 14
    One of the most famous early “scientific” texts relates to epilepsy. Epilepsy had traditionally been known as “the sacred disease,” because its sudden onset and violent nature suggested an act of the gods, yet in a text attributed to Hippocrates, probably from the early fourth century B.C., the writer states:
    I do not believe that the so-called “Sacred Disease” is any more divine or sacred than any other diseases. It has its own specific nature and cause; but because it is completely different from other diseases men through their inexperience and wonder at its peculiar symptoms have believed it to be of divine origin . . . [yet] it has the same nature as other diseases and a similar cause. It is also no less curable than other diseases unless by long lapse of time it is so ingrained that it is more powerful than the drugs that are applied. Like other diseases it is hereditary . . . The brain is the cause of the condition as it is of other most serious diseases... 15
    Here we have not only the specific rejection of the divine as a cause but a sophisticated attempt based on observation to say something about the real nature of epilepsy, its causes and its cures. It should be stressed, however, that the rejection of divine intervention did not mean a rejection of the gods themselves. The famous Hippocratic oath, which probably dates from the beginning of the fourth century, requires the physician to swear by the gods Apollo, Asclepius and Asclepius’ two daughters, Hygeia and Panacea. It was rather that the sphere of activity of the gods was diminished and there was greater reluctance, at least among intellectuals, to see natural events as caused by them. Alternatively, they could be seen as the forces that set in motion the regularity with which the natural world operates.
    In dealing with the natural world, whether it be the universe, material objects such as earth and water, plants, animals or human beings themselves, the Greeks