An advisor or counselor, someone who provides guidance in matters requiring wisdom and decision-making. Paul quotes Isaiah 40:13 in Romans 11:34: 'Who has been his counselor?'—a rhetorical question emphasizing that God needs no human advisor. The term was used for political and military advisors in Greek literature, as well as for official Roman legates. Paul's use underscores God's complete independence: the creator of all wisdom requires no consultant to inform his decisions about Israel's salvation or the inclusion of the Gentiles.