The current debate between realists and anti-realists has brought to the fore some ancient questions about the coherence of relativism. Realism is the doctrine according to which the truth of sentences is determined by the way things really are. Truth is thus the result of a relation between sentences and reality. One species of anti-realism holds, on the contrary, the truth results from a relation between sentences within a theory: a sentence is true if warranted by a correct theory.