All sacrifices and offerings required an accompanying prayer to be effective. Pliny the Elder declared that "a sacrifice without prayer is thought to be useless and not a proper consultation of the gods." Prayer by itself, however, had independent power. The spoken word was thus the single most potent religious action, and knowledge of the correct verbal formulas the key to efficacy. Accurate naming was vital for tapping into the desired powers of the deity invoked, hence the proliferation of cult epithets among Roman deities. Public prayers (prex) were offered loudly and clearly by a priest on behalf of the community. Public religious ritual had to be enacted by specialists and professionals faultlessly; a mistake might require that the action, or even the entire festival, be repeated from the start. The historian Livy reports an occasion when the presiding magistrate at the Latin festival forgot to include the "Roman people" among the list of beneficiaries in his prayer; the festival had to be started over. Even private prayer by an individual was formulaic, a recitation rather than a personal expression, though selected by the individual for a particular purpose or occasion.