In order to make this clear, I must call your attention to a double aspect possessed by all beliefs alike, whatever be the subject-matter with which they deal. All beliefs have a position, actually or potentially, in a cognitive series; all beliefs, again, have a position, known or unknown, in a causal series. All beliefs, in so far as they belong to the first kind of series, are elements in one or more collections of interdependent propositions. They are conclusions, or premises, or both. All beliefs, in so far as they belong to the second kind of series, are elements in the temporal succession of interdependent events. They are causes, or effects, or both. It has, further, to be noted that whereas reasons may, and usually do, figure among the proximate causes of belief, and thus play a part in both kinds of series, it is always possible to trace back the causal series to a point where every trace of rationality vanishes; where we are left face to face with conditions of beliefs—social, physiological, and physical—which, considered in themselves, are quite a-logical in their character. It is on this last point that I particularly desire to insist. We are all very familiar with the equivocal origin of most human creeds. To be sure, we observe it chiefly in the case of other people. In our own case, we dwell by preference on those causes of our beliefs which are also reasons. But in our detached studies of the opinions we do not share, we easily perceive how insufficient are the arguments officially urged on their behalf, and how often even these insufficient arguments have only a nominal connection with the convictions of which they claim the legal paternity. We must, however, go yet one step further. We must realise that, on any merely naturalistic hypothesis, the rational elements in the causal series lie always on the surface. Penetrate but a short way down, and they are found no more. You might as easily detect life in the minerals wherein plants are rooted, as reason in the physiological and physical changes to which the source of our most carefully reasoned beliefs must, in the last resort, be traced.