IT is a matter of general agreement that there is no disputing about facts. Facts exert a kind of compulsion over us, and we feel that the person who will not accept something which is "as plain as the nose on one's face" is peculiarly obstinate and irritating. But while it is true that we feel under obligation to accept facts we also recognize that the problem of determining whether what appears to be a fact really is a fact is frequently a troublesome one. We all believe that grass is green and that two plus two equals four; about such facts there seems no ground for dispute, since "seeing is believing." Yet we should not forget the amazing deceptions produced by magicians and sleight-of-hand performers. That the United States participated in the first World War from 1917 to 1918 would probably be questioned by no one, since it happened within the memory of many who are alive today; but that Columbus discovered America in 1492 or that Homer existed may be called into question, since they rest only on historical evidence. Finally, in our knowledge of the future, and in certain areas of science, e.g., the possible relation between smoking and cancer of the lung, or the cause of gene mutations, no one is in a position to state what the facts are.
Very early in man's historical development he recognized the need for a standard by which he could discriminate between genuine facts and apparent ones. His very survival depended upon his ability to distinguish foods from poisons, substances which were useful for tools and weapons from those which were not, friendly animals and peoples from unfriendly ones, and so on. Gradually there emerged, through trial and error, a method for acquiring beliefs and testing them for validity. This is now called "intelligence" and it constitutes the main advantage which modern man possesses over the animals, who must act by instinct and conditioned response, and over primitive man, who relied on magic and superstition.