David Hartley

“ The understanding is that faculty by which we contemplate mere sensations and ideas, pursue truth, and assent to, or dissent from, propositions.
The affections have the pleasures and pains for their objects; as the understanding has the mere sensations and ideas. By the affections we are excited to pursue happiness, and all its means, and to fly from misery, and all its apparent causes. ”

“ The motions of the body are of two kinds, automatic and voluntary. The automatic motions are those which arise from the mechanism of the body in an evident manner. They are called automatic, from their resemblance to the motions of automata, or machines, whose principle of motion is within themselves. Of this kind are the motions of the heart, and peristaltic motion of the bowels. The voluntary motions are those which arise from ideas and affections, and which therefore are referred to the mind ”

“ The pleasures and pains are comprehended under the sensations and ideas, as these are explained above. For all our pleasures and pains are internal feelings, and conversely, all our internal feelings seem to be attended with some degree either of pleasure or pain. ”