John Locke said that reason consists of two parts. First, an inquiry to what things we know with certainty. Second, an investigation into propositions which are wise to accept in practice even though they are probable and not certain.
The grounds of probability are two – conformity with our own experience or testimony of other people’s experience.
Happiness and pleasure moves people, motivates them. It is only in the long run that self interest and general interest coincide, man should be prudent. Prudence leads to wealth, impudence to poverty.
But pleasure isn’t primary according to Russell. We gain pleasure by doing what we find desirable, we don’t seek pleasure on its own. Even the masochist gains pleasure through the gratification of a desire, or the opposite of pleasure.
Locke’s argument is that we desire pleasure but most men desire proximate pleasure not distant pleasure.