I have been touching the edge of certain problems of great interest but enormous complexity, and I shall venture to indicate the difference between these views and some which have recently attracted much attention. Mr. Kidd's work upon "Social Evolution" has made the phrase popular; but, instead of using it in my sense, he speaks as though "social evolution" involved what I have called individual evolution. In order to keep within limits, I will confine myself to one case upon which he lays great stress. It will show sufficiently why I hold his mode of reasoning to be inconclusive. Mr. Kidd has achieved success by very excellent qualities, by remarkable literary ability, and by his uniformly high tone of moral feeling. I should, therefore, be very sorry to speak of him otherwise than respectfully. Mr. Kidd, however, chooses to maintain a thesis in which he has certainly no personal interest,--the thesis, namely, that a little stupidity may be a very good thing. This view is, perhaps, intelligible when we observe that he also maintains that the progress of the race depends upon its holding "ultra-rational," which I think he would find it hard to distinguish from "irrational," beliefs. In support of this view he writes a chapter to prove that "progress is not primarily intellectual". The argument of which I have spoken is part of this proof. The Greeks, he tells us, were a race intellectually superior to ourselves. They were, so Mr. Galton informs him, two degrees above modern Englishmen in the scale of intelligence, and as superior to us as we are to the negro. And yet, says Mr. Kidd, this marvellous race died out, and no trace of its blood is now to be found in the present population of the world. Let us look shortly into the logic of this argument, and consider how far it is entitled to be regarded as scientific reasoning.