In view of this fact of mutual participation of nature and idea among the sciences that use each other, I have myself conceived, and in another place have given expression to, what appropriately may be called a physical psychology or epistemology.'[1] This new hybrid science is especially concerned with nothing more nor less than those substitutes, disguises, or [p.093] indirections, really present in all the physical sciences, for the peculiar nature, for the peculiar sort of unity, intensive instead of extensive or qualitative instead of quantitative, or say also even vital and spiritual instead of physical, which is always associated with mind. In conservation of matter, energy, what you will, in plenitude, in motion as only relative and so as always under a principle of uniformity and constancy or even immobility, in motion too as inclining to vibration, which suggests poise or tension, or to rotation, in which we see rest as well as motion, and finally, not to extend what might be a long list, in the infinity of space and time or of quantity, the physical sciences have hidden entrances for the silent, usually unnoticed admission of what is psychical. But I may seem to be jumping too far, to be presuming too much. Then put the case in this way--not quite so direct, but to the same goal. All of these conceptions, so necessary to a "working" physical science, need very little examination to be seen to be treacherous to the physical standpoint and its peculiar categories. One might as well try to make water unsupported assume definiteness of form as to conceive the conservation of energy or plenitude or the relativity of motion in the character of what is physical, or at least of what is properly and conventionally physical. Being treacherous, then, to the physical science that has conceived them, they are, as was said, doors for what is not physical; hidden doors, perhaps, but certainly doors to be opened at will; and by them mind is bound to enter the physical world and its sciences. To those familiar with the history of philosophy, the speculation [p.094] of the early Greek thinkers, notably Anaximander, Parmenides, and Anaxagoras, will afford illustration of the physical view running, in spite of itself, into treacherous conceptions, and eventually reaching the discovery of their treachery and with it the idea of mind or _Nous_.[2]