These are problems concerning which innocent people might imagine that the wise refrained from speculating, but, as a matter of fact, the various groups of philosophic devotees may be divided into those termed “Idealists” and those termed “Realists,” each assured of the superiority of his own way of viewing thought. Roughly speaking, for the idealist thought means the creation of the world, for the realist its discovery. But here (as in many differences between Tweedledum and Tweedledee for which men have slain one another these thousands of years) there seem to be superiorities on both sides. Each looks at thought in a different aspect. But the idealist could hardly create the world with nothing there to make it from, nor the realist discover it save through creating it afresh. We cannot, so to put it, express in a single formula of three dimensions what only exists as a unity in four dimensions. Footnote 147: Bertrand Russell, _Principles of Social Reconstruction_ (1916), p. 235. Footnote 148: I may here be allowed to refer to another discussion of this point, Havelock Ellis, _The Philosophy of Conflict, and Other Essays_, pp. 57-68. Footnote 149: I may remark that Plato had long before attributed the same observation to the Pythagorean Timæus in the sublime and amusing dialogue that goes under that name: “Sight in my opinion is the source of the greatest benefit to us, for had we never seen the stars, and the sun, and the heavens, none of the words which we have spoken about the universe would ever have been uttered. But now the sight of day and night, and the months and the revolution of the years, have created Number, and have given us a conception of Time, and the powers of inquiring about the Nature of the Universe, and from this source we have derived philosophy, than which no greater good ever was or will be given by the gods to mortal man.” Footnote 150: Jules de Gaultier, “La Guerre et les Destinées de l’Art,” _Monde Nouveau_, August, 1920. Footnote 151: Thus Einstein, like every true man of science, holds that cultural developments are not to be measured in terms of utilitarian technical advances, much as he has himself been concerned with such advances, but that, like the devotee of “Art for Art’s sake,” the man of science must proclaim the maxim, “Science for Science’s sake.” Footnote 152: In the foregoing paragraphs I have, in my own way, reproduced the thought, occasionally the words, of Jules de Gaultier, more especially in “La Moralité Esthétique” (_Mercure de France_, 15th December, 1921), probably the finest short statement of this distinguished thinker’s reflections on the matter in question. Footnote 153: Guyau, _L’Art au Point de Vue Sociologique_, p. 163. Footnote 154: