Again, like the principle of Causality, the principle of Uniformity may be successful to different degrees, according to the special nature of the processes for which it is assumed. As the causal postulate rested on the assumption that a selection from the antecedents of an event may for practical purposes be treated as equivalent to its complete ground, so the more general postulate of Uniformity rests on the assumption that individual purpose may be left out of account in assigning the ground of a process. It does not follow that these postulates will receive the same amount of empirical justification for all departments of the physical order. There may well be certain processes in which the individual purposive character is so prominent that, even for our practical purposes, we cannot safely calculate their course without taking their end or purpose into consideration. In that case the principle of Uniformity and that of Causality would, for this part of the physical order, lose their practical value. It is a popular belief that such a failure of these practical postulates actually takes place where we come to deal with the conscious volitions of human agents. The problem is one which must be kept for fuller consideration in our next Book, but we can at present make two general statements. (1) Such a failure of the postulates of Causality and Uniformity in application to a particular sphere would not involve a breach of the fundamental logical principle of Ground and Consequence, since, as we have seen sufficiently already, both postulates impose special restrictions on that principle for which the nature of the principle itself affords no warrant. It would thus not be an unthinkable or logically untenable position to hold that no general laws of human action can be formulated.