David Hume and the eighteenth-century conception of natural law

Natural law is discussed by almost every modern writer on jurisprudence; but with a few exceptions - of which John Finnis' Natural Law and Natural Rights is the most substantial - the impression given is that it is of historical interest only, that it has in some way been discredited, or at least superseded, by legal positivism. The implicit idea - and here legal positivism borrows from Comte - is that natural law represented some earlier ‘metaphysical’ stage which was then followed by ‘scientific’ legal positivism. This account requires the existence of a natural law theory that dominated juristic and philosophical thinking until the eighteenth century, when it was overthrown by Hume and Bentham. Hume, the story goes, found the decisive argument against the natural law theory; while Bentham created the new theory oflegal positivism. The argument Hume discovered was that ought cannot be derived from is; and this, it is widely supposed, is fatal to all varieties of natural law.