Ordinarily pleasure and pain are regarded as different from sensations.

Physics is experience, arranged in economical order.

Without renouncing the support of physics, it is possible for the physiology of the senses, not only to pursue its own course of development, but also to afford to physical science itself powerful assistance.

Similarly, many a young man, hearing for the first time of the refraction of stellar light, has thought that doubt was cast on the whole of astronomy, whereas nothing is required but an easily effected and unimportant correction to put everything right again.

Man is pre-eminently endowed with the power of voluntarily and consciously determining his own point of view.

Scientists must use the simplest means of arriving at their results and exclude everything not perceived by the senses.

I once knew an otherwise excellent teacher who compelled his students to perform all their demonstrations with incorrect figures, on the theory that it was the logical connection of the concepts, not the figure, that was essential.