that these loans really belong to the state of science thirty or forty yeats earlier. The presuppositions of the physics of my boyhood are to-day powertul influences in the mentality of physiologists. Indeed, we do not aeed even to bring in the physiologists. The presuppositions of yesterday’s physics remain in the minds of physicists, although their explicit doctrines taken in detail deny them.
In order to understand this sporadic interweaving of old and new in modern thought, I will recur to the main principles of the old common-sense doctrine, which even to-day is the common doctrine of ordinary life because in some sense it is true. There are bits of matter, enduring self-identically in space which is otherwise empty. Each bit of matter ccupies a definite |imited region. Each such particle of matter has its own private qualifications — such as its shape, its motion, its mass, its colour, its scent. Some of these
