But the world was not standing still, and during the next thirty years many things happened. Vaihinger found the new sect of Pragmatists coming into fashion with ideas resembling his own, though in a cruder shape, which seemed to render philosophy the “meretrix theologorum.” Many distinguished thinkers were working towards an attitude more or less like his own, especially Nietzsche, whom (like many others even to-day) he had long regarded with prejudice and avoided, but now discovered to be “a great liberator” with congenial veins of thought. Vaihinger realised that his conception was being independently put forward from various sides, often in forms that to him seemed imperfect or vicious. It was no longer advisable to hold back his book. In 1911, therefore, “Die Philosophie des Als Ob” appeared. The problem which Vaihinger set out to solve was this: How comes it about that with consciously false ideas we yet reach conclusions that are in harmony with Nature and appeal to us as Truth? That we do so is obvious, especially in the “exact” branches of science. In mathematics it is notorious that we start from absurdities to reach a realm of law, and our whole conception of the nature of the world is based on a foundation which we believe to have no existence. For even the most sober scientific investigator in science, the most thoroughgoing Positivist, cannot dispense with fiction; he must at least make use of categories, and they are already fictions, analogical fictions, or labels, which give us the same pleasure as children receive when they are told the “name” of a thing. Fiction is, indeed, an indispensable supplement to logic, or even a part of it; whether we are working inductively or deductively, both ways hang closely together with fiction; and axioms, though they seek to be primary verities, are more akin to fiction. If we had realised the nature of axioms, the doctrine of Einstein, which sweeps away axioms so familiar to us that they seem obvious truths, and substitutes others which seem absurd because they are unfamiliar, might not have been so bewildering.