On the other hand, it need not be disputed that unbelief has been often enough associated with some species of libertinism to give a passing colour for the pretence of causal connection. The fact, however, leads us to a less superficial explanation, worth keeping in view here. Freethinking being taken to be normally a "variation" of intellectual type in the direction of a critical demand for consistency and credibility in beliefs, its social assertion will be a matter on the one side of force of character or degree of recklessness, and on the other hand of force of circumstances. The intellectual potentiality and the propagandist purpose will be variously developed in different men and in different surroundings. If we ask ourselves how, in general, the critical tendency is to arise or to come into play, we are almost compelled to suppose a special stimulus as well as a special faculty. Critical doubt is made possible, broadly speaking, by the accumulation of ideas or habits of certain kinds which insensibly undo a previous state of homogeneity of thought. For instance, a community subsiding into peace and order from a state of warfare and plunder will at length find the ethic of its daily life at variance with the conserved ethic of its early religion of human sacrifice and special family or tribal sanctions; or a community which has accumulated a certain amount of accurate knowledge of astronomy will gradually find such knowledge irreconcilable with its primitive cosmology. A specially gifted person will anticipate the general movement of thought; but even for him some standing-ground must be supposed; and for the majority the advance in moral practice or scientific knowledge is the condition of any effective freethinking.