abhors a fallacy or a fiction more than a vacuum; and though for a stated period the true cause of a given phenomenon may be hidden from view, owing to the imperfect means or the imperfect intelligence employed to unravel it, and thus a fictitious origin be assigned for it, yet in course of time the error is sure to be detected and the truth to be revealed. Thus it was with the astronomical system of Ptolemy. Up to the time of Copernicus the learned world as well as the illiterate were led to believe that the sun and all the rest of the heavenly bodies revolved around the earth, as the center of the entire system. Yet, as soon as the error was exploded, and the truth demonstrated, there was a universal rejection of the one and a universal recognition of the other. So, at a later period, when the true theory of ethereal undulations, as applied to light, fought its way against much opposition into popular belief, the old theory of emanations was dropped, never to be again taken up.
Nevertheless, from what has been said, it must not be inferred that what are called coincidences of thought never occur among scientists. On the contrary, these are so common as to give license for believing in the existence of a law, akin to that of evolution if not a part of it, by virtue of which, in the progress of knowledge, certain new truths dawn upon the world, receiving expression simultaneously from more than one mind. Given the age which is ripe for any discovery, and it breaks out in many different quarters of the globe at the same moment. Men seem to be watching for it, and, like a meteor glancing across the heavens, it is witnessed by several observers from many points of the compass. Take, for example, the great law of natural selection, as applicable to man's origin—it was discovered simultaneously in England by Darwin and Wallace; while in Germany, at the same time, Haeckel had promulgated a similar theory; and in France, in a preceding age, Lamarck had laid the foundation for it in the most unmistakable manner.
But it is only in this single point of occasional coincidence or identity that the leading thoughts of science take on a certain likeness with those of literature. The analogy ends with the admission that each of these thoughts may have rival paternities. Beyond this the difference becomes manifest; and it consists in this: While the utterances of different literatures may seem to be original, this is often owing to a variation in their phraseology, an examination of which will show them to be identical; and, in addition to this, there is no criterion by which their truth can be tested. But in science, while different claims may be made for originality of discovery, each truth stands out in bold relief, is distinct and well defined, and, after it has been submitted to all the various verifications of which it is susceptible, it no longer admits of any doubt and becomes a part of the common stock of human knowledge, possessing, as nearly as possible, the attributes of positive, absolute, and immutable truth.
