Vaihinger... shows that thought is primarily a biological function turned into a conscious art. It is an art of adjustment, whose chief instrument is the construction of fictions by which men may manage to live. Thought is to be tested not by correspondence to an objective reality (that fiction is neatly disposed of) nor by its mirroring in consciousness an objective external world. Thought is to be tested by its fruits. The constructions of thought are not copies of or transcripts of reality; they are programs, guess-work plans; possible programs for operation. Their validity is to be measured not by verisimilitude but by value. The fruits of thought are not "true," but especially where they are false, it may be important to act as if they were true... Vaihinger's chief originality consists in his defining of fictions and his distinction of fictions from hypotheses on the one hand, and from dogmatisms on the other. An hypothesis is a tentative discovery about the universe; a fiction is a deliberate, often clearly false and internally contradictory invention of thought... Evolution is the hypothesis that man is descended from the lower animals. We assume that we can indirectly turn to the remote facts which would justify that hypothesis. But the concept of infinity in the calculus, the atom and the ether in physics, the economic man in Adam Smith, are deliberate self-contradictory fictions, and fictions at variance with all experience. But though they are not only imaginary, false to the reality they allegedly represent and logically incoherent, they nevertheless facilitate thought and proper action. They are vital lies, human conveniences. They are the faiths, the palpably false faiths, the clearly useful falsities by which we live... The discovery that fictions were fictions has led, in the past, says Vaihinger, to an abandonment of them, and a turning to other fictions believed to be truer. Pathetic and foolish adventure! What the race needs is more faith in its own effective imaginations. The myths that it has told itself, the world pictures that it has made, are not to be dismissed because they are found to be creations of the imagination. They tally with no world and they carry the canker of logical inconsistency within them. The important thing is their utility; their human scope and mortal relevance. If we ceased making fictions, we should cease altogether to be. Let us beware to plunge from fruitful fictions to less fruitful ones that masquerade as truths and are really dogmatisms. (Review of As If by Irwin Edman, Saturday Review of Literature, 10 January, 1925) This is a well-formatted version of C.K. Ogden's translation of Philosophie des Als Ob, originally published in 1925 by Kegan Paul.