As soon as the ideas of reality and unreality are once formed, ample opportunity is found for their application. They are applied also to cases which do not belong to either of the extremes of vividness, permanence, and distinctness, or feebleness, fleetingness, and vagueness. Finally, they are applied by mere analogy to cases which do not directly call for their application--as in a discussion of historical truths. At this point another distinction is made. Trees with leaves of silver are never presented to our sense organs. But the elements which make up even the most contradictory compounds of fancy have been known through the sense organs and become known again as sensory impressions. Trees with a foliage of silver are not seen in everyday life; but trees are seen, and leaf-like things of silver, too. Even if all our ideational thought were fancy, its elements would tend to make us conscious of the concept of reality rather than of unreality because separately the elements have often been experienced with a high degree of vividness, permanence, and distinctness. The opportunities for thinking of reality are incomparably more numerous in human life than those for thinking of unreality. We develop the habit of conceiving our thoughts as real, unless there is a positive force compelling us to accept the opposite concept. Thus we understand why the child, as soon as he has formed these two concepts, is immensely credulous. Tell the child that the moon is going to drop from heaven, and he will look up, expecting to see it fall. The child’s experience is limited. There is but rarely a positive force tending to reproduce in his consciousness the concept of unreality. Where there is no such force, the child does not remain neutral, skeptical, but conceives his thought as including objective reality. Language assists in this tendency, for the first words acquired by the child mean objective realities, persons, clothes, furniture, and so on. The frequent use of these words strengthens the habit of thinking of things as realities. Of much influence is also the use of the verb _to be_ as a mere copula and also in the sense of _to exist_. The child is thus induced to regard a thing as existing because it is thought _to be_ yellow, round, etc. That _to be_ is used in this ambiguous manner in all languages seems to be additional proof of what is historically certain, that the human race, like the human child, has passed through a period of extreme credulity. This racial credulity through the traditional usage of language contributes now to the credulity of the individual.