The
identity of indiscernibles is an
ontological principle that states that there cannot be separate
objects or
entities that have all their
properties in common. That is, entities
x and
y are identical if every
predicate possessed by
x is also possessed by
y and vice versa; to suppose two things indiscernible is to suppose the same thing under two names. It states that no two distinct things (such as
snowflakes) can be exactly alike, but this is intended as a metaphysical principle rather than one of natural science. A related principle is the indiscernibility of identicals, discussed below.