Page:Mind (New Series) Volume 9.djvu/406

 392 CRITICAL NOTICES : tion that the actual direction of motion differentiates itself from all the others by its uniqueness. It is only this uniqueness that gives to the actual change its right to be actualised, its right to be chosen hi preference to any other possible change. Thus a ball moving freely on a horizontal plane passes from -D AB on to C, A "R^T ^- ^ m igh* conceivably have passed from B to D, but though this course is a thinkable one it is not realised, because its realisation would involve an ambiguity, for no reason could then be given why the direction BD was chosen in preference to the symmetrical direction BE. The direction BC is in this case the only one that is unique and therefore unambiguous. The third element, that of continuity, secures the possibility of exact quantitative determination. The fundamental law of unideterminateness is formally enun- ciated by Mr. Petzoldt in the following words : ' For every occur- rence, means of determination can be discovered whereby the occurrence is unambiguously determined, in this sense, that for every deviation from it, supposed to be brought about through the same means, at least one other could be found which being determined in the same way would be its precise equivalent, and have as it were precisely the same right to be actualised ' (p. 39). By ' means of determination ' are meant just those means e.g., masses, velocities, temperatures, distances by the help of which we are able to grasp an occurrence as singled out by its uniqueness from a number of equally thinkable occur- rences. This unideterminateness of things is both a fact of Nature and the a priori logical condition of there being a cosmos at all instead of a chaos. Our thought demands it from Nature, and Nature invariably justifies the demand. It is the one necessary and sufficient condition of explanation. An occurrence is explained when it is shown to be unidetermined. Otherwise, it is not only not explained, but is inexplicable. In this one supreme fact of the unideterminateness of all things the mind finds its rest. It is an ultimate fact (Thatsache), and you can no longer ask Why? when you come to ultimate facts. Beyond this pure actuality no further problem lies concealed : thought can only state its presence and accept its meaning. But this does not imply that thought is baffled by an impenetrable fact; it implies only that on reaching its ideal of unideterminateness it finds that the facts do not enable it to pierce any further. It comes to rest in its own interests just where any further movement is impossible by the very nature of things. Having defined and established the fundamental principle of unideterminateness Mr. Petzoldt proceeds to show (1) that as a matter of fact psychical processes do not determine each other