stylistic:style_transfer, information:classification, stylistic:tone, information:filtering, linguistic:voice_change
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Identity is a relation that every entity has to itself as a form of sameness. It refers to numerical identity when the very same entity is involved, as in the statement "the morning star is the evening star " (both are the planet Venus). In a slightly different sense, it encompasses qualitative identity, also called exact similarity and indiscernibility, which is the case when two distinct entities are exactly alike, such as perfect identical twins. The principle of the indiscernibility of identicals is widely accepted and holds that numerically identical entities exactly resemble one another. The converse principle, known as identity of indiscernibles or Leibniz's Law, is more controversial and states that two entities are numerically identical if they exactly resemble one another. Another distinction is between synchronic and diachronic identity. Synchronic identity relates an entity to itself at the same time while diachronic identity is about the same entity at different times, as in statements like "the table I bought last year is the same as the table in my dining room now". Personal identity is a related topic in metaphysics that uses the term identity in a slightly different sense and concerns questions like what personhood is or what makes someone a person.

Various contemporary metaphysicians rely on the concepts of truth, truth-bearer, and truthmaker to conduct their inquiry. Truth is a property of being in accord with reality. Truth-bearers are entities that can be true or false, such as linguistic statements and mental representations. A truthmaker of a statement is the entity whose existence makes the statement true. For example, the statement "a tomato is red" is true because there exists a red tomato as its truthmaker. Based on this observation, it is possible to pursue metaphysical research by asking what the truthmakers of statements are, with different areas of metaphysics being dedicated to different types of statements. According to this view, modal metaphysics asks what makes statements about what is possible and necessary true while the metaphysics of time is interested in the truthmakers of temporal statements about the past, present, and future.