[3] It is curious that the attempt to show that Plato’s opponents were not commonly illusive and immoral reasoners, has been represented as an attempt to obliterate the distinction of “Sophist” and “Philosopher.”—See A. Butler’s Lectures, i. 357. Note.
That these two classes of teachers, as moralists, were not different in their kind, has been urged by Mr. Grote in a very striking and amusing manner. But Bacon speaks of them here as physical philosophers; in which character he holds that all of them were sophists, that is, illusory reasoners.
Aristotle’s Account of the Rainbow.
To exemplify the state of physical knowledge among the Greeks, we may notice briefly Aristotle’s account of the Rainbow; a phenomenon so striking and definite, and so completely explained by the optical science of later times. We shall see that not only the explanations there offered were of no value, but that even the observation of facts, so common and so palpable, was inexact. In his Meteorologica (lib. iii. c. 2) he says, “The Rainbow is never more than a semicircle. And at sunset and sunrise, the circle is least, but the arch is greatest; when the sun is high, the circle is larger, but the arch is less.” This is erroneous, for the diameter of the circle of which the arch of the rainbow forms a part, is always the same, namely 82°. “After the autumnal equinox,” he adds, “it appears at every hour of the day; but in the summer season, it does not appear about noon.” It is curious that he did not see the reason of this. The centre of the circle of which the rainbow is part, is always opposite to the sun. And therefore if the sun be more than 41° above the horizon, the centre of the rainbow will be so much below the horizon, that the place of the rainbow will [496] be entirely below the horizon. In the latitude of Athens, which is 38°, the equator is 52° above the horizon, and the rainbow can be visible only when the sun is 11° lower than it is at the equinoctial noon. These remarks, however, show a certain amount of careful observation; and so do those which Aristotle makes respecting the colors. “Two rainbows at most appear: and of these, each has three colors; but those in the outer bow are duller; and their order opposite to those in the inner. For in the inner bow the first and largest arch is red; but in the outer bow the smallest arch is red, the nearest to the inner; and the others in order. The colors are red, green, and purple, such as painters cannot imitate.” It is curious to observe how often modern painters disregard even the order of the colors, which they could imitate, if they attended to it.
It may serve to show the loose speculation which we oppose to science, if we give Aristotle’s attempt to explain the phenomenon of the Rainbow. It is produced, he says (c. iv.), by Reflexion (ἀνάκλασις) from a cloud opposite to the sun, when the cloud forms into drops. And as a reason for the red color, he says that a bright object seen through darkness appears red, as the flame through the smoke of a fire of green wood. This notion hardly deserves notice; and yet it was taken up again by Göthe in our own time, in his speculations concerning colors.
BOOK II.
THE PHYSICAL SCIENCES IN ANCIENT GREECE.