There is a classical statement: while natural science has as its objects things that repeat themselves, historical science deals with unique events. This is why the former is said to be a nomothetic science and the latter idiographic science. But such a scheme of division seems to me too rigorous and too formalist. To be sure a historical survey of the philosophy of history in Europe reveals some such metaphysical premise peculiar to Christianity, but this premise is of such a nature that we cannot reasonably prove it. The idealistic philosophers of history have tried to draw out the absolute nature of history from it, and consequently fallen into an exaggerated sort of spiritualism and intuitionism. Is there no way to grasp the uniqueness of history but by telepathy ? Our answer to this question runs as follows : 1. The "uniqueness" of history is not a simple quality which each historical event possesses, but the uniqueness of interest or standpoint which characterizes each historian. 2. So it is something relative. 3. Moreover the historian makes use of universallaws and general terms in his unique individual descriptions. 4. The historical events themselves do not in any way exclude the possibility of being generalized, of being, that is, viewed as repeating themselves. On the other hand, historical science should not be regarded in the same light as natural and social sciences, nor is it a mere application of the latter. Explanation in historical science does not stand on the same level as explanation in science. In contrast to the latter which always explains in terms of instance and generalization, the former does so in terms of theme and illustration. Thus in this paper we seek to find the true nature of historical explanation between idealism and scientism.