T 2.3.5.3

By degrees the repetition produces a facility, which is another very powerful principle of the human mind, and an infallible source of pleasure, where the facility goes not beyond a certain degree. And here 'tis remarkable that the pleasure, which arises from a moderate facility, has not the same tendency with that which arises from novelty, to augment the painful, as well as the agreeable affections. The pleasure of facility does not so much consist in any ferment of the spirits, as in their orderly motion; which will sometimes be so powerful as even to convert pain into pleasure, and give us a relish in time for what at first was most harsh and disagreeable.