V THE BEGINNINGS OF GREEK SCIENCE A History of Science: in Five Volumes. Volume I: The Beginnings of Science | ||
5. V
THE BEGINNINGS OF GREEK SCIENCE
HERODOTUS, the Father of History, tells us that once upon a time—which time, as the modern computator shows us, was about the year 590 B.C. —a war had risen between the Lydians and the Medes and continued five years. "In these years the Medes often discomfited the Lydians and the Lydians often discomfited the Medes (and among other things they fought a battle by night); and yet they still carried on the war with equally balanced fortitude. In the sixth year a battle took place in which it happened, when the fight had begun, that suddenly the day became night. And this change of the day Thales, the Milesian, had foretold to the Ionians, laying down as a limit this very year in which the change took place. The Lydians, however, and the Medes, when they saw that it had become night instead of day, ceased from their fighting and were much more eager, both of them, that peace should be made between them.''
This memorable incident occurred while Alyattus, father of Crœsus, was king of the Lydians. The modern astronomer, reckoning backward, estimates this eclipse as occurring probably May 25th, 585 B.C. The date is important as fixing a mile-stone in the chronology of ancient history, but it is doubly memorable because it is the first recorded instance of a
Such citations as these serve to bring vividly to mind the fact that we are entering a new epoch of thought. Hitherto our studies have been impersonal. Among Egyptians and Babylonians alike we have had to deal with classes of scientific records, but we have scarcely come across a single name. Now, however, we shall begin to find records of the work of individual investigators. In general, from now on, we shall be able to trace each great idea, if not to its originator, at least to some one man of genius who was prominent in bringing it before the world. The first of these vitalizers of thought, who stands out at the beginnings of Greek history, is this same Thales, of Miletus. His is not a very sharply defined personality as we look back upon it, and we can by no means be certain that all the discoveries which are ascribed to him are specifically his. Of his individuality as a man we know
All of this, however, must not be taken as casting any doubt upon the existence of Thales as a real person. Even the dates of his life—640 to 546 B.C.— may be accepted as at least approximately trustworthy; and the specific discoveries ascribed to him illustrate equally well the stage of development of Greek thought, whether Thales himself or one of his immediate disciples were the discoverer. We have already mentioned the feat which was said to have given Thales his great reputation. That Thales was universally credited with having predicted the famous eclipse is beyond question. That he actually did predict it in any precise sense of the word is open to doubt. At all events, his prediction was not based upon any such precise knowledge as that of the modern astronomer. There is, indeed, only one way in which he could have foretold the eclipse, and that is through knowledge of the regular succession of preceding eclipses. But that knowledge implies access on the part of some one to long series of records of practical observations of the heavens. Such records, as we have seen, existed in Egypt and even more notably in Babylonia. That these records were the source of the information which established the reputation of Thales is an unavoidable inference. In other words, the magical prevision of the father of Greek thought was but a reflex of Oriental wisdom. Nevertheless, it sufficed to establish Thales as the father of Greek astronomy. In point of fact, his actual astronomical attainments
When we turn to the other field of thought with which the name of Thales is associated—namely, geometry—we again find evidence of the Oriental influence. The science of geometry, Herodotus assures us, was invented in Egypt. It was there an eminently practical science, being applied, as the name literally suggests, to the measurement of the earth's surface. Herodotus tells us that the Egyptians were obliged to cultivate the science because the periodical inundations washed away the boundary-lines between their farms. The primitive geometer, then, was a surveyor. The Egyptian records, as now revealed to us, show that the science had not been carried far in the land of its birth. The Egyptian geometer was able to measure irregular pieces of land only approximately. He never fully grasped the idea of the perpendicular as the true index of measurement for the triangle, but based his calculations upon measurements of the actual side of that figure. Nevertheless, he had learned to square the circle with a close approximation to the truth, and, in general, his measurement sufficed for all his practical needs. Just how much of the geometrical
- That the circle is bisected by its diameter.
- That the angles at the base of an isosceles triangle are equal.
- That when two straight lines cut each other the vertical opposite angles are equal.
- That the angle in a semicircle is a right angle.
- That one side and one acute angle of a right-angle triangle determine the other sides of the triangle.
It was by the application of the last of these principles that Thales is said to have performed the really notable feat of measuring the distance of a ship from the shore, his method being precisely the same in principle as that by which the guns are sighted on a modern man-of-war. Another practical demonstration which Thales was credited with making, and to which also his geometrical studies led him, was the measurement of any tall object, such as a pyramid or building or tree, by means of its shadow. The method, though simple enough, was ingenious. It consisted merely in observing the moment of the day when a perpendicular stick casts a shadow equal to its own length. Obviously the tree or monument would also cast a shadow
All that we know of the psychology of Thales is summed up in the famous maxim, "Know thyself,'' a maxim which, taken in connection with the proven receptivity of the philosopher's mind, suggests to us a marvellously rounded personality.
The disciples or successors of Thales, Anaximander and Anaximenes, were credited with advancing knowledge through the invention or introduction of the sundial. We may be sure, however, that the gnomon, which is the rudimentary sundial, had been known
It is said that Anaximander departed from Thales's conception of the earth, and, it may be added, from the Babylonian conception also, in that he conceived it as a cylinder, or rather as a truncated cone, the upper end of which is the habitable portion. This conception is perhaps the first of these guesses through which the Greek mind attempted to explain the apparent fixity of the earth. To ask what supports the earth in space is most natural, but the answer given by Anaximander, like that more familiar Greek solution which transformed the cone, or cylinder, into the giant Atlas, is but another illustration of that substitution of unwarranted inference for scientific induction which we have already so often pointed out as characteristic of the primitive stages of thought.
Anaximander held at least one theory which, as vouched for by various copyists and commentators, entitles him to be considered perhaps the first teacher
(p. 111). Anaximander, as recorded by Plutarch, Symp. VIII., 730E. See Arthur Fairbanks' First Philosophers of Greece: an Edition and Translation of the Remaining Fragments of the Pre-Socratic Philosophers, together with a Translation of the more Important Accounts of their Opinions Contained in the Early Epitomes of their Works, London, 1898. This highly scholarly and extremely useful book contains the Greek text as well as translations.
V THE BEGINNINGS OF GREEK SCIENCE A History of Science: in Five Volumes. Volume I: The Beginnings of Science | ||