Ethos is a Greek word originally meaning "accustomed place". Ethos forms the root of ethikosis, meaning "moral, showing moral character". To the Greeks ancient and modern, the meaning is simply "the state of being", the inner source, the soul, the mind, and the original essence, that shapes and forms a person or animal. Late Latin borrowed it as ethicus, the feminine of which is the origin of the modern English word ethics.

In rhetoric, ethos is one of the three artistic proofs modes of persuasion (other principles being logos and pathos) discussed by Aristotle in 'Rhetoric' as a component of argument. At first speakers must establish ethos. On the one hand, this can mean merely "moral competence", but Aristotle broadens this word to encompass expertise and knowledge. He expressly remarks that ethos should be achieved only by what the speaker says, not by what people think of his character before he begins to speak. This position is often disputed and other writers on rhetoric state that ethos is connected to the overall moral character and history of the speaker.

According to Reynolds, "ethos, like postmodern subjectivity, shifts and changes over time, across texts, and around competing spaces." However, Reynolds additionally discusses how one might clarify the meaning of ethos within rhetoric as expressing inherently communal roots. This stands in direct opposition of what she describes as the claim "that ethos can be faked or 'manipulated'" because individuals would be formed by the values of their culture and not the other way around. While its meaning and application within literature might differ over time, this classical interpretation remains the same.

There are three categories of ethos, which, if followed in the situation of speaking, could help develop a high ethos:

* phronesis - practical skills & wisdom
* arete - virtue, goodness
* eunoia - goodwill towards the audience

It is important to note that ethos does not belong to the speaker, but to the audience. Thus, it is the audience that determines whether a speaker is a high- or a low-ethos speaker. Violations of ethos can entail some of the following:

* The speaker has a direct interest in the outcome of the debate (e.g. a person pleading innocence of a crime);
* The speaker has a vested interest or ulterior motive in the outcome of the debate;
* The speaker has no expertise (e.g. a lawyer giving a speech on space flight carries less gravity than an astronaut giving the same speech)

It should be noted that dismissing an argument based on any of the above violations of ethos is a formal fallacy, rendering the dismissal of the argument invalid. The term "source credibility" has been used as the construct examined in the social sciences. Though recent work has found support for the existence of the three dimensions identified above, work from the 1950s through the 1980s consistently revealed two dimensions - competence and character with other dimensions such as dynamism found only when broad approaches equating credibility with "person perception" were taken. - excerpt from Wikipedia

Example:

"If, in my low moments, in word, deed or attitude, through some error of temper, taste, or tone, I have caused anyone discomfort, created pain, or revived someone's fears, that was not my truest self. If there were occasions when my grape turned into a raisin and my joy bell lost its resonance, please forgive me. Charge it to my head and not to my heart. My head - so limited in its finitude; my heart, which is boundless in its love for the human family. I am not a perfect servant. I am a public servant doing my best against the odds." - Jesse Jackson, Democratic National Convention Keynote Address, 1984