Page:Philosophical Review Volume 1.djvu/286

270 space. "Airy" is a synonym for "unreal," "imaginary." Yet to the scientific mind, air is real and space-filling, besides being not unimportant to human life. To the scientific mind the space between our earth's atmosphere and the stars is not empty, but filled by what is called the luminiferous æther. To the unscientific mind this does not seem to be real quite in the same way as stone or clay is real. The more resisting seems the more real. "Solidity" and "reality" are used as convertible terms.

III. Our attention is thus called conspicuously to the fact that the real world of ordinary belief and the real world of scientific belief are very different. Colors, sounds, etc., are translated into their physiological and then into their physical "causes" ; i.e. they are represented as movements in space. The primary qualities of matter thus seem, from the scientific point of view, to have greater reality than the secondary. Not that which is felt, but that which can be thought in terms of mathematical conceptions, has the greater reality to the scientific mind. A thing really is — that way of thinking about it which fits it into its place in an intelligible system of the universe.

This difference between ordinary and scientific reality is not the antithesis between the "phenomenal" and the "real." The real with which science has to do is what would be the phenomenal, if we had keener vision, etc.; e.g. what appears at rest to the naked eye is seen to be in motion if we look through a microscope. If by reality were meant things-in-themselves, and not phenomena or possible phenomena, then reality would be identical with the unknowable. Ultimate reality may be the unknowable to us, as well as the unknown, but it must be that which would appear to a being possessing complete knowledge. Complete knowledge is to us a mere ideal: but the most real world we can know must be what the world means when we come to think it out. Thus when science comes to put aside any theory, such as, e.g. the corpuscular theory of light, this means that the light corpuscles are considered unreal, because their existence conflicts with the less rapid transmission of light in water than in a vacuum, etc. The logical tests of the value