Aristotle believed that through the use of the rhetorical process
Truth and justice may be guarded against falsehood and wrong.
Debate may be conducted on subjects in the absence of absolute truth.
Both sides of a claim may be presented.
Proof to establish the probability of a position may be developed.
These four aspects of the rhetorical process described by Aristotle are still in use today. Aristotle's persuasion involves the use of three elements of proof: logos, pathos, and ethos.
Logos Means logic and is the use of reason to support a decision. Logical appeals essentially present the situation, the alternatives, and the set of probabilities involved in the decision-making process. Such appeals are directed to our mind's reasoning capabilities.
Pathos Means emotion and is the use of emotional and motivational appeals to support a decision. Emotional appeals are directed to the wishes, wants, desires, goals, and needs of the person, whose acceptance is desired. Such appeals are directed to the heart.
Ethos Refers to the use of source credibility to support a conclusion. Aristotle perceived ethos as a powerful proof supplied by the source himself, and through which judgments could be made about his character, wisdom, and goodwill. The argument is accepted due to the character of the person arguing. Aristotle wrote,
"Persuasion is achieved by the speaker's personal character where the speech is so spoken as to make us think him credible. We believe good men more fully and more readily than others; this is true generally whatever the question is, and absolutely true where exact certainty is impossible and opinions are divided. This kind of persuasion, like the others, should be achieved by what the speaker says, not by what people think of his character before he begins to speak." 1
Ethos is thus the image of the source held in the mind(s) of the audience. Source credibility can be developed in two ways:
The first type is called initial ethos. This ethos is based on the arguer's credentials, status, and reputation, as known to the audience before they hear or read the content of the message. Advertisers have increasingly turned to “positive image makers” to sell their clients' products. The idea is if you like them, you will be favorably disposed toward the product they are endorsing.
The second type is called derived ethos. This is the speaker’s credibility that is created during the message. You may not know much about the presenter, but as you listen to the argument you find yourself more and more impressed with him or her. Derived ethos is created from both the content of the presentation and the style of the speaker. In a job interview, you want to create a positive derived ethos as you make your “argument” that you should be hired.
A minimal level of positive ethos is necessary for logical and emotional proofs to achieve effectiveness. Low credibility sources cannot use high levels of emotional appeals effectively, because the audience doesn’t believe in the source in the first place. Likewise, lacking a certain minimal ethos, logical proof will be ignored, because the source is not perceived as a person who is trustworthy.
Aristotle and C.D.C.Reeve, Aristotle's The Rhetoric, (Indianapolis: Hackett Publishing Company Inc. 2018)