We know what wood is and what earth and stone are and that they have a color and texture, a smell and even a taste, but matter as a perceptible material substance independent of the nature of the wood, earth and stone composed of it seems incomprehensible. In order for us to regard a thing as real it must possess at least some distinctive physical qualities. We must be able to experience it as a physical thing before we can decide it is real. Matter as proposed by modern science, however, has no distinctive or definite physical qualities at all. Matter is simply some unimaginable stuff possessing no conceivable definition whatsoever. The concept of matter, then, proves to be just as elusive and abstract as the concepts of spirit, soul or the life-principle.