Persuasion rests on the speaker's credibility, the audience's feeling, and the argument itself; neglecting any one loses the audience.
Aristotle's three appeals, from the Rhetoric. His subtler point is that ethos is largely constructed within the speech itself rather than brought to it.
In practice
- A pitch with faultless numbers and no established credibility loses to one where the audience already trusts the speaker.
- A safety briefing that is accurate, and delivered by someone the crew does not respect, changes no behaviour.