  What is it for something to be itself by itself and/or  in relation to other things (for a detailed discussion of  this distinction, see Dancy 1999)? The traditional understanding of  the distinction relies on a passage from Diogenes Laertius (first  half of the 3rd century CE). Diogenes uses the expression  “in relation to something” (pros ti) in place of “in relation to other things” (pros alla):