By this term I designate principally, not exclusively, what ordinary speech calls "inspiration." In spite of its mysterious and semi-mythological appearance, the term indicates a positive fact, one that is ill-understood in a deep sense, like all that is near the roots of creation. This concept has its history, and if it is permissible to apply a very general formula to a particular case we may say that it has developed according to the law of the three states assumed by the positivists. In the beginning, inspiration is literally ascribed to the gods--among the Greeks to Apollo and the Muses, and in like manner under various polytheistic religions. Later, the gods become supernatural spirits, angels, saints, etc. In one way or another it is always regarded as external and superior to man. In the beginnings of all inventions--agriculture, navigation, medicine, commerce, legislation, fine arts--there is a belief in revelation; the human mind considers itself incapable of having discovered all that. Creation has arisen, we do not know how, in a total ignorance of the processes. Later on these higher beings become empty formulas, mere survivals; there remain only the poets to invoke their aid, through the force of tradition, without believing in them. But side by side with these formal survivals there remains a mysterious ground which is translated by vague expressions and metaphors, such as "enthusiasm," "poetic frenzy," "possession by a spirit," "being overcome," "having the devil inside one," "the spirit whispers as it lists," etc. Here we have come out of the supernatural without, however, attempting a positive (i.e., a scientific) explanation. Lastly, in the third stage, we try to sound this unknown. Psychology sees in it a special manifestation of the mind, a particular, semi-conscious, semi-unconscious state which we must now study. At first sight, and considered in its negative aspect, inspiration presents a very definite character. It does not depend on the individual will. As in the case of sleep or digestion, we may try to call it forth, encourage it, maintain it; but not always with success. Inventors, great and small, never cease to complain over the periods of unproductiveness which they undergo in spite of themselves. The wiser among them watch for the moment; the others attempt to fight against their evil fate and to create despite nature. Considered in its positive aspect, inspiration has two essential marks--suddenness and impersonality.