Early in Romans, Paul gives two definitions of 'gospel.' The ancient philosophical and rhetorical theory on definition instructs that it should concisely state the essence and function of the definiendum. Robert Matthew Calhoun shows that Paul's definitions conform closely to this instruction. In 1:2-4, the apostle declares the essence of the gospel as Christ's fulfillment of God's promises in the scriptures. In 1:16-17, he specifies its function as God's power for salvation, and as the agent of the revelation of divine justice. Paul utilizes sophisticated tactics of brevity, and he exploits ambiguities in the terminology and syntax. These strategies enable him to return to his definitions in his subsequent arguments in order to recombine their component terms, bringing forward latent meanings and implications.