Moral philosophy, or the science of human nature, may be treated after two different manners; each of which has its peculiar merit, and may contribute to the entertainment, instruction, and reformation of mankind. The one considers man chiefly as born for action; and as influenced in his measures by taste and sentiment; pursuing one object, and avoiding another, according to the value which these objects seem to possess, and according to the light in which they present themselves.

Este libro ha ejercido una gran influencia, tanto en la epoca en la que se lo publico como en la actualidad. Hume afirma que todo conocimiento deriva, en ultima instancia, de la experiencia sensible, siendo esta la unica fuente de conocimiento y sin ella no se lograria saber alguno.