During the past century and a quarter science has remodeled man's universe. In this period, so short that many of us have talked with those who saw its onset, more significant discoveries have been made than in all previous ages combined. One cannot picture vividly the vast changes induced by probing the secrets of atom, molecule, and cell. Comfortable dwellings, luxurious journeys, instantaneous communication, sanitary conditions, longer and healthier spans of life, economic and intellectual freedom, are accepted casually, without emotion, without thanksgiving. We think of them as part of our natural environment - like clouds or sunshine or green trees. But conditions were quite different at the beginning of the nineteenth century, so different that an evening with the most impressively written history of the time fails to carry us back and to identify us with the situation that confronted our great-grandparents. Perhaps a visit to central Africa might do it, but few of us have such an opportunity.

Unfortunately science has not recast man's thinking to anything like the same degree. The average mind is still fettered to myths conceived in distant eras of unreason. The proportion of persons guided by rational ideas has certainly increased in recent years; but an intellectual lag obtains which shows in even the best of us. The trouble is that the whole world profits from all new discoveries, yet only the exceptional few care about the philosophy of thought which makes them possible.

Intelligence tests carried on in the more enlightened countries during the past two decades have shown that fully fifty per cent of the people involved lack the capacity to follow even elementary scientific reasoning. This fact is often accepted as evidence that the scientific outlook can appeal to only a small fraction of the population. No conclusion could be more superficial. The average mind, the mean mind, as the statistical wag puts it, absorbs teaching to the limit of its power. It is conditioned by its experience, as all minds are conditioned by experience. But where the superior mind is compelled - lso by training - to sift its varied grist of lore, holding fast that which is good, the untrained or inferior mind takes in more indiscriminately whatever is offered of digestible quality. The reason the brains of most people are stuffed with so much medieval nonsense, therefore, is that this is the intellectual fodder with which they have been supplied. Clearly, then, if progress in the world of ideas is to keep pace with material progress, these thob-fancies must be replaced by ascertained truth.

Can it be done? Well, why not? Have we no leaders of thought? Can we make no changes in our educational system? It is very difficult to alter the mores of a people, as Sumner has shown in that noble treatise "Folkways" yet it is not impossible. The soviet rulers are doing it rapidly and thoroughly. It is true that here one set of foolish ideas is being replaced with another; but this fact is of little consequence. The important thing is the demonstration that success is possible in such an undertaking. My personal belief and, I think, the universal belief of all true men of science, is that humanity can aspire to nothing more lofty or more satisfactory than a philosophy based solely on demonstrated truth. I should like to see a world in which people endeavor to deal only with facts, all the facts, and nothing but the facts; where truth is approached without prejudice, and the course of action to which it leads is faced without evasion. I believe that it would be a more comforting as well as a more comfortable world.

Such creedal statements immediately stimulate emotional reactions in people whose minds have fixations on the mystical. Before they burst forth in criticism or denunciation, I have always wished that they would answer one question: Is it or is it not a worthy objective to prefer truth to falsehood? But they are too cunning to be caught in such a simple trap. Instead, they suggest that the above doctrine is "the substance of things hoped for," and therefore a faith rather than a belief; they say that they also are seekers after truth, but that their brand of verity includes subjective truth, intuitive truth; and they maintain that numerous able scientists hold similar opinions.

H. L. Mencken, with his usual forcefulness, has shown the absurdity of the mystics who thunder against the beliefs of men of science as being indistinguishable from articles of faith. "Belief is faith in something that is known," says he, "faith is belief in something that is not known." The distinction is good; and by it the faith of the scientific man in objective truth, established by impartial evidence and demonstrable to all who have been taught the use of reason, becomes a belief. The basis for it is the fact that the whole course of human progress has been due wholly and solely to the use of scientific methodology. There is no more justification for faith in intuition than for faith in witches. Intuition is merely a delusive word for something that wishful thinkers hope for, a phantom to enable them to vindicate their own irrationality. There are instincts, it is true, but experimental physiology has shown that instincts are drives which are tropistic in nature and which have little connection with the higher cerebral centers. They should not be confounded with intuitions. For example, certain larvae, which hatch in loam, make their way immediately to the tree tops. But they do not take this journey because their brains tell them, in some mysterious intuitive way, that food is there. They go because their optical outfit is so constituted that they are driven toward the light. Desensitize their eyes, and they starve to death, though a well-filled larder is near at hand.