The search after adequate causes is everywhere given as a necessity of thought wherever mental life is found. An adequate cause is required for “that which is,” just as much as for “that which happens”; it is that which both presume. _To possess a world-theory and therewith a world-conception means to comprehend adequate causes._ According to the attitude assumed by mental life toward the question of adequate causes, does it separate off in two main directions: the direction of faith and the direction of science. II FAITH AND A WORLD-THEORY _There is present a something given--the world._ It presents itself as an endlessly vast sum of processes. Where there is a process there is happening. Where something happens, there adequate causes are demanded. Every attempt to comprehend adequate causes leads backwards in endless series, since each cause comprehended is something which itself in turn demands an adequate cause, and so on backwards without ever a conclusion. _Faith_ is that particular form of mental life which from this fact draws the inference that for the human mind a real comprehension is impossible, since behind the physical there stands a something transcendent, a force, with reference to which all life-phenomena become that which their name expresses: _phenomena of a “life”_ which faith for the most part designates by the word “_god_.” This force stationed behind the physical, to which faith traces back all that happens, must be an “adequate cause in itself,” hence something contrary to sense in the fullest meaning of the words. For all that is, without exception, requires an adequate cause. An “adequate cause in itself” would thus be that something which by its simple existence would give the lie to this thought-necessity, inasmuch as itself would be that which would have no adequate cause. When the thought-necessity of an adequate cause is thus satisfied with an “adequate cause in itself,” this just means: it is satisfied _in a fashion contrary to sense_. The essence of all that is contrary to sense consists in this, that when followed out in thought, it deprives itself of the possibility of existence. A mistake in an arithmetical sum is the most familiar form of what is contrary to sense. It is something that in correct thinking is by itself deprived of all possibility of existence; it is something that makes its appearance only that it may appear no more.