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7. The Name of Apollo: Etymology and Essence*
ἠπείλησεν μῦθον, ὃ δὴ τετελεσμένος ἐστί
and boastfully promised [verb apeiléō] a mūthos,  which now has come to fulfillment [=verb teléō, from noun télos ‘fulfillment’].
In such contexts, the word apeiléō designates the actual performance of a speech-act, a mūthos, while the word teléō, derivative of télos ‘fulfillment’ guarantees that the speech-act is really a speech-act, in that the course of events, which amounts to actions emanating from the speech-act, bears out the speech-act. We may compare the Homeric instances where apeiléō can be translated as ‘vow’ in the context of prayers addressed to gods (Iliad XXIII 863, 892).  In such cases the course of events in the future is predicated on the value of the words spoken as a speech-act: if a god hears a prayer, then the words spoken as prayer are a speech-act, and then the actions promised by the one who prays can bear out the speech-act. Conversely, it is implicit that if a god does not hear a prayer, then the words spoken as prayer are not really a prayer: they turn out to have been not a speech-act after all, and the actions promised by the one who intended a prayer need not be carried out. I submit that the god who primarily presides over speech-acts, which are then ratified by the actual course of events, is Apollo. It is for this reason that he presides over oracles, including the great Oracle at Delphi.