What is it for a truth to be true? What makes it true? This is one of the oldest problems in philosophy and one to which Armstrong turned in Truth and Truthmakers. His concern was not with the epistemological question of how we know some particular statement or utterance to be true or false, but in what truth itself and falsehood itself actually consist. Armstrong's concern was therefore with the metaphysics of truth.

As Armstrong is a realist and naturalist, we are not surprised to find that he opts for something akin to the correspondence theory of truth: “propositions correspond or fail to correspond to reality” (T&T: 16). The correspondence theory has faced much criticism throughout its history: see for example Lewis (2001) but also M. David's (2004) reply. Critics of the theory have demanded that it be made more substantial. What are the two things that enter into correspondence, what is the correspondence relation, and how are these two different things able to correspond in the required way? (For more on the theory, see Engel 2002.) Truthmaker theory is an attempt to answer these questions and make the correspondence theory substantial. It is, however, a characteristically Australian take on the correspondence theory, which Armstrong credits to C. B. Martin's residence at the University of Adelaide.

The requirement for truthmakers has been encountered already in Chapters 5 and 8, on dispositions and the materialist theory of mind.