Truthmaker theory is "the branch of metaphysics that explores the relationships between what is true and what exists".[1] The basic intuition behind truthmaker theory is that truth depends on being. For example, a perceptual experience of a green tree may be said to be true because there actually is a green tree. But if there were no tree there, it would be false. So the experience by itself does not ensure its truth or falsehood, it depends on something else. Expressed more generally, truthmaker theory is the thesis that "the truth of truthbearers depends on the existence of truthmakers". A perceptual experience is the truthbearer in the example above. Various representational entities, like beliefs, thoughts or assertions can act as truthbearers. Truthmaker theorists are divided about what type of entity plays the role of truthmaker; popular candidates include states of affairs and tropes.
Truthmaker maximalism is the thesis that every truth has a truthmaker. An alternative view is truthmaker atomism, the thesis that only atomic sentences have truthmakers. Truthmaker atomism remains true to the basic intuition that truth depends on being by holding that the truth of molecular sentences depends on the truth of atomic sentences, whose truth in turn depends on being. All non-maximalist positions accept that there are truthmaker gaps: truths without truthmakers. Opponents have tried to disprove truthmaker theory by showing that there are so-called deep truthmaker gaps: truthbearers that not only lack a truthmaker but whose truths do not even depend on being. Various principles governing the truthmaking relation have been proposed in order to make the intuitions about the role and nature of truthmaking explicit. Truthmaker theory is closely related to the correspondence theory of truth, but not identical to it. Truthmaker theory has been applied to various fields in metaphysics, often with the goal of exposing ontological cheaters: theorists who are committed to certain beliefs but do not or cannot account for the existence of a truthmaker for these beliefs.