The Symposium on the “ Colour-problem,” recently organized by our Institute and published in this Journal, deserved to be welcomed, not only for the intrinsic importance of its topic, but also as an indication that it is the policy of the Institute not to restrict philosophy to purely theoretical questions. This is a return to the Platonic tradition which lays upon the philosopher the obligation to descend from the sunlit world of pure theory into the dark cave of practice. It is a much needed reminder to our “ practical ” age (which has some respect for science, but little, if any, for philosophy), that where practice touches on fundamental human values, it will fail of wisdom and, therefore, of the highest success without that illumination of experience which philosophy alone can give.