never been any conflict between religion and science, nor is any reconciliation called for where harmony has always existed. The real historical conflict, which has been thus curiously misnamed, has been the conflict between the more-crude opinions belonging to the science of an earlier age and the less-crude opinions belonging to the science of a later age. In the course of this contest the more-crude opinions have usually been defended in the name of religion, and the less-crude opinions have invariably won the victory; but religion itself, which is not concerned with opinion, but with the aspiration which leads us to strive after a purer and holier life, has seldom or never been attacked. On the contrary, the scientific men who have conducted the battle on behalf of the less-crude opinions have generally been influenced by this religious aspiration quite as strongly as the apologists of the more-crude opinions, and so far from religious feeling having been weakened by their perennial series of victories, it has apparently been growing deeper and stronger all the time. The religious sense is as yet too feebly developed in most of us; but certainly in no preceding age have men taken up the work of life with more earnestness or with more real faith in the unseen than at the present day, when so much of what was once deemed all-important knowledge has been consigned to the limbo of mythology. The more-crude theories of early times are to be chiefly distinguished from the less-crude theories of to-day as being largely the products of random guesswork. Hypothesis, or guesswork, indeed, lies at the foundation of all scientific knowledge. The riddle of the universe, like less important riddles, is unravelled only by approximative trials, and the most brilliant discoverers have usually been the bravest guessers. Kepler's laws were the result of indefatigable guessing, and so, in a somewhat different sense, was the wave-theory of light. But the guesswork of scientific inquirers is very different now from what it was in older times. In the first place, we have slowly learned that a guess must be verified before it can be accepted as a sound theory; and, secondly, so many truths have been established beyond contravention, that the latitude for hypothesis is much less than it once was. Nine tenths of the guesses which might have occurred to a mediaeval philosopher would now be ruled out as inadmissible, because they would not harmonize with the knowledge which has been acquired since the Middle Ages. There is one direction especially in which this continuous limitation of guesswork by ever-accumulating experience has manifested itself. From first to last, all our speculative successes and failures have agreed in teaching us that the most general principles of action which prevail to-day, and in our own corner of the universe, have always prevailed throughout as much of the universe as is accessible to our research.