From The Art and Popular Culture Encyclopedia The fact-value
distinction is a concept used to distinguish between arguments
that can be claimed through reason alone and those in which
rationality is limited to describing a collective opinion. In
another formulation, it is the distinction between what is (can
be discovered by science, philosophy or reason) and what ought
to be (a judgment which can be agreed upon by consensus). The
terms positive and normative represent another manner of
expressing this, as do the terms descriptive and prescriptive,
respectively. Positive statements make the implicit claim to
facts (e.g. water molecules are made up of two hydrogen atoms
and one oxygen atom), whereas normative statements make a claim
to values or to norms (e.g. water ought to be protected from
environmental pollution).