Human Nature
For Bentham, morals and legislation can be described scientifically, but such a description requires an account of human nature. Just as nature is explained through reference to the laws of physics, so human behaviour can be explained by reference to the two primary motives of pleasure and pain; this is the theory of psychological hedonism.
There is, Bentham admits, no direct proof of such an analysis of human motivation--though he holds that it is clear that, in acting, all people implicitly refer to it. At the beginning of the Introduction to the Principles of Morals and Le…