But Knowledge—the department of human interest to which I now turn—is differently placed. The values with which we shall be concerned are mainly rational; and intellectual curiosity is the only emotion with which they are associated. Yet here also two questions arise corresponding to those which we have already dealt with in a different connection: (1) what are the causes of our knowledge, or of that part of our knowledge which concerns the world of common sense and of science? (2) does the naturalistic account of these causes affect the rational value—in other words the validity—of their results? We are, perhaps, more sensitive about the pedigree of our intellectual creed than we are about the pedigree of our tastes or our sentiments. We like to think that beliefs which claim to be rational are the product of a purely rational process; and though, where others are concerned, we complacently admit the intrusion of non-rational links in the causal chain, we have higher ambitions for ourselves. Yet surely, on the naturalistic theory of the world, all such ambitions are vain. It is abundantly evident that, however important be the part which reason plays among the immediate antecedents of our beliefs, there are no beliefs which do not trace back their origin to causes which are wholly irrational. Proximately, these beliefs may take rank as logical conclusions. Ultimately, they are without exception rooted in matter and motion. The rational order is but a graft upon the causal order; and, if Naturalism be true, the causal order is blind. III Before I further develop this line of speculation it may help you to understand what I am driving at if I venture upon an autobiographical parenthesis. The point I have just endeavoured to make I have made before in these lectures, and I have made it elsewhere. It is one of a number of considerations which have led me to question the prevalent account of the theoretical ground-work of our accepted beliefs. Taken by itself, its tendency is sceptical; and, since it has been associated with arguments in favour of a spiritual view of the universe, I have been charged (and not always by unfriendly commentators) with the desire to force doubt into the service of orthodoxy by recommending mankind to believe what they wish, since all beliefs alike are destitute of proof. As we cannot extricate ourselves from the labyrinth of illusion, let us at least see to it that our illusions are agreeable. This, however, is not what I have ever wanted to say, nor is it what I want to say now. If I have given just occasion for such a travesty of my opinions, it must have been an indirect consequence of my early, and no doubt emphatically expressed, contempt for the complacent dogmatism of the empirical philosophy, which in Great Britain reigned supreme through the third quarter of the nineteenth century. But was this contempt altogether unreasonable?