widely different paths, the visual, tactual, and auditory sensations which the soul then combines into the idea of a trumpet. Thus, what is really the result of a process (i.e., the idea of a trumpet), is for my consciousness the primary datum. In this result nothing can any longer be found of what exists outside of me and originally stimulated my sense-organs. The external object is lost entirely on the way to the brain and through the brain to the soul. It would be hard to find in the history of human speculation another edifice of thought which has been built up with greater ingenuity, and which yet, on closer analysis, collapses into nothing. Let us look a little closer at the way it has been constructed. The theory starts with what is given in naïve consciousness, i.e., with things as perceived. It proceeds to show that none of the qualities which we find in these things would exist for us, had we no sense-organs. No eye--no colour. Therefore, the colour is not, as yet, present in the stimulus which affects the eye. It arises first through the interaction of the eye and the object. The latter is, therefore, colourless. But neither is the colour in the eye, for in the eye there is only a chemical, or physical, process which is first conducted by the optic nerve to the brain, and there initiates another process. Even this is not yet the colour. That is only produced in the soul by means of the brain process. Even then it does not yet appear in consciousness, but is first referred by the soul to a body in the external world. There I finally perceive it, as a quality of this body. We have travelled in a complete circle. We are conscious of a coloured object. That is the starting-point. Here thought begins its construction. If I had no eye, the object would be, for me, colourless. I cannot, therefore, attribute the colour to the object. I must look for it elsewhere. I look for it, first, in the eye--in vain; in the nerve--in vain; in the brain--in vain once more; in the soul--here I find it indeed, but not attached to the object. I recover the coloured body only on returning to my starting-point. The circle is completed. The theory leads me to identify what the naïve man regards as existing outside of him, as really a product of my mind.