You might think so if you had a look in Merriam Webster:
ethos (n.): The distinguishing character, sentiment, moral nature, or guiding beliefs of a person, group, or institution.
What's wrong with simply saying character or moral nature, for heaven's sake? Aren't those better choices?
Yes: for that definition. But there is a particular use of the word ethos that MW doesn't tackle head-on. And for this use, really, no synonym quite does the job.
Ethos is one of the three modes of persuasion that Aristotle lists in On Rhetoric. (The other two are logos and pathos, but I'll leave those for now.) As a mode of persuasion, ethos is appeal to authority. You hear speakers (and read writers) do this all the time. They do it when they argue that they are suitable to represent their position:
- I've been an MP in this riding for 12 years and I know my constituents: they don't want a needle-exchange program.
- I'm a tenured professor in Stanford's philosophy department, and I say the ontological argument for the existence of God stinks, I tell you, it stinks!
- As your doctor, I should tell you that all that echinacea tea you're drinking isn't doing a darned thing.
Notice that none of these statements above makes any argument for the truth of their claims other than a simple appeal to the authority—the credibility—of the speaker. It's not enough to establish the truth of a proposition, but it is often persuasive.
So why do I murmur ethos quietly to myself from time to time?
Because if we don't have sufficient authority ourselves (damn! I'm not an MP/tenured philosophy professor at Stanford/doctor!), we borrow it. I do it all the time:
- Studies have shown...
- My mum says...
- Everybody knows...
(And here's a recent example, which is what got me thinking about this tonight.)
I have to watch it; someone may catch on. But keep in mind that you can't really dismiss an argument because you don't think the speaker has sufficient ethos. (Well, you can, but you shouldn't.) You have to look at how the argument hangs together logically. And that's logos.... (at least that's what the experts tell me) and maybe I'll talk about that another time.
**Wait, wait, waaaaaaaaaaait a minute—I already have stopped getting invited to parties. Damn! It's 'cause I said semiotics once, right? I can't believe you heard that. But that was only a joke! Honest! I wouldn't know a semiotics if it stood up in my soup!