This acknowledgment of personal and of historical life by philosophy makes it intelligible why philosophy manifests so much diversity and opposition, and why on the surface it shows so little unity. Where the conviction of an independent spiritual life rules, the faith in a unity of truth can be shaken by this fact just as little as the courage to creative activity can be paralysed. The basing of thought upon the spiritual life also has the advantage that the main types of thought can be derived from the different positions which may be taken up towards the spiritual life, and thus a limit may be set to the otherwise indefinite abundance. From this point of view there are for us five chief types of thought and world-conception. Minds first divide on the question whether we can unify life at all, and at the same time whether we may venture to make an assertion concerning reality as a whole. He who rejects this as impossible and readily surrenders himself to the conflict of immediate impressions might be called an indifferentist. If, however, a striving towards unity is admitted, then the question whether a spiritual life with a reality and values of its own in contrast with nature may be acknowledged or not becomes the point of decision, and the basis of division into opposing camps. He who gives a negative answer to the question, and regards nature as the whole of reality, becomes an advocate of Naturalism. He, however, who answers in the affirmative, and may be called an idealist, is immediately confronted with a new problem. He cannot acknowledge the spiritual life without at the same time giving it the supremacy; but now the doubt arises whether this supremacy may be easily and peacefully established, or whether it meets with strong opposition. When the existence of these oppositions is denied, or they are regarded as being easy to overcome, there grows up an optimistic, contemplative form of Idealism, which to the holders of other forms inevitably seems abstract and shallow. If, on the contrary, the oppositions are fully acknowledged, the final division originates with the question whether finally we are to submit to the state of stagnation brought about by these oppositions, or whether by some kind of reinforcement of the counteraction to this state of stagnation life may once more be set in progress: the former gives rise to Scepticism and Pessimism, the latter to Activism, as it has been discussed by us in an earlier section. It is easy to see what distinctive lines of conflict and what kinds of conflict must arise between the indifferentist, the naturalistic thinker, the optimist, the sceptic, and the activist. However, we cannot allow this to detain us; it must, nevertheless, be pointed out here, that in philosophy the possibilities are not yet exhausted, and that to avail ourselves of these possibilities nothing is more necessary than a close relation of its work with the life-process,