Using the Hilbert-Bernays account as a spring-board, we first define four ways in which two objects can be discerned from one another, using the non-logical vocabulary of the language concerned. Because of our use of the Hilbert-Bernays account, these definitions are in terms of the syntax of the language. But we also relate our definitions to the idea of permutations on the domain of quantification, and their being symmetries. These relations turn out to be subtle---some natural conjectures about them are (...) false. We will see in particular that the idea of symmetry meshes with a species of indiscernibility that we will call `absolute indiscernibility'. We then report all the logical implications between our four kinds of discernibility. We use these four kinds as a resource for stating four metaphysical theses about identity. Three of these theses articulate two traditional philosophical themes: viz. the principle of the identity of indiscernibles, and haecceitism. The fourth is recent. Its most notable feature is that it makes diversity weaker than what we will call individuality : two objects can be distinct but not individuals. For this reason, it has been advocated both for quantum particles and for spacetime points. Finally, we locate this fourth metaphysical thesis in a broader position, which we call structuralism. We conclude with a discussion of the semantics suitable for a structuralist, with particular reference to physical theories as well as elementary model theory. (shrink)

This article for the Stanford Encyclopedia for Philosophy provides a state of the art survey and assessment of the contemporary debate about truth-makers, covering both the case for and against truth-makers. It explores 4 interrelated questions about truth-makers, (1) What is it to be a truth-maker? (2) Which range, or ranges, of truths are eligible to be made true (if any are)? (3) What kinds of entities are truth-makers? (4) What is the motivation for adopting a theory of truth-makers? And (...) adds that there's another question to often put aside by metaphysicians but has critical consequences for truth-makers: (5) What are the truth-bearers? (shrink)