The
is-ought problem, as articulated by Scottish
philosopher and
historian David Hume (1711–76), states that many writers make claims about what
ought to be on the basis of statements about what
is. Hume found that there seems to be a significant difference between descriptive statements (about what is) and prescriptive or
normative statements (about what ought to be), and that it is not obvious how one can coherently move from descriptive statements to prescriptive ones. The is–ought problem is also known as
Hume's law, or
Hume's guillotine.