The student of history discovers a law underlying the undulating motions of human thought which is known as the law of recurrence. In accordance with it, attention, interest, enthusiasm and allegiance tend to swing back and forth like the pendulum of the old hall clock between different and even conflicting in terpretations and applications of world-facts and world-forces. The tide of individual and race interest ebbs and ?ows. It has always been so, it will con tinue to_ be so; two psychological facts produce this perpetual motion in mental mechanics — 'the natural aversion to monotony which familiarity produces, and on the other hand, the increasing tyranny of cus tom, popular Opinion and human authority, growing finally into intolerance and over-pressure, from which wholesale revolt is inevitable sooner or later. Now such a ?uctuation is illustrated in the regular swing between idealism and materialism, the one reading the literature of being in terms of spirit, the other in terms of matter. The tide of idealistic inter pretation has come in with such thinkers as Plato, Plotinus, Berkeley, Kant; and has gone outwith the coming of such as Epicurus, Zeno, Spencer, Haeckel. Today there is a widespread and thqoroughgoing re volt against materialism with its Gospel of Dirt according to Carlyle. And one of the forms in which this revolt manifests itself is in the strenuous applica tion of psychical forces for the manipulation and alteration of physical conditions. Mind has gone up a good many points in the intellectual stock exchange, While matter is away down below par and selling slow. Thought-force has suddenly become a popular therapeutic agency.