indiscernibility of identicals

English

(philosophy) The principle that if two objects are absolutely identical then they must be indistinguishable from one another with respect to all of their properties.
- 1943, Willard V. Quine, “Notes on Existence and Necessity”, in The Journal of Philosophy, volume 40, number 5, page 113:
  One of the fundamental principles governing identity is that of substitutivity—or, as it might well be called, that of indiscernibility of identicals. It provides that, given a true statement of identity, one of its two terms may be substituted for the other in any true statement and the result will be true.
- 2004, Peter Alward, “The Spoken Work”, in The Journal of Aesthetics and Art Criticism, volume 62, number 4, page 335:
  For example, Levinson claims that a Stamitz symphony containing a "Manheim rocket"—a novel device in Stamitz's day—is an exciting musical work, but a work written today with the same sound structure would be funny rather than exciting. Since the Stamitz symphony and the (hypothetical) contemporary sound-identical work differ in properties, it follows from the indiscernibility of identicals that they are distinct musical works.