Aristotle hoped than mankind would embrace the logic of the syllogism and the enthymeme for making arguments. While he recognized the need for, and importance of, emotional appeals, he claimed that the affairs of mankind should be handled through logic. You will recognize the syllogism as the old "fluffy is a mammal" argument. It goes like this:
All cats are mammals.
Fluffy is a cat.
Therefore, fluffy is a mammal.
The enthymeme is the rhetorical syllogism, in which part of the logical sequence is left unstated. For example:
Some politicians are corrupt.
Therefore, Senator Jones could be corrupt.
Edward P. J. Corbett described the difference between syllogism and enthymeme this way: "[T]he syllogism leads to a necessary conclusion from universally true premises but the enthymeme leads to a tentative conclusion from probable premises. In dealing contingent human affairs, we cannot always discover or confirm what truth is."
The problem with Aristotle's logic (concerning his desire for logic) is that argument by the syllogism is often deadly dull. Humans are passionate creatures whose hearts and minds are moved with appeals to emotion (pathos), character (ethos), as well as logic (logos). The rhetorician must decide the proper balance of these appeals in the presentation of any argument.
Forms of Argument
Aristotle’s Artistic Proofs
How do arguments persuade? Aristotle said that rhetors persuade by effective use of "proofs" or "appeals." He divided proofs into two classes: 1) the inartistic proofs that one simply uses for inductive arguments (e.g. statistics), and 2) the artistic proofs that one must create.
Logos: appeals to reason
Such an appeal attempts to persuade by means of an argument “suitable to the case in question,” according to Aristotle. Appeals to logos most often use the syllogism and enthymeme. You may recognize the syllogism as the formal method of deductive reasoning (see above). The enthymeme is a truncated syllogism, also referred to as the rhetorical syllogism, in which one or more minor premises are left unstated. You may recognize the enthymeme as assertions followed by reasons. We rarely find syllogisms in their pure form in civic discourse. Instead, we find statements and reasons that are incomplete and are therefore enthymemes. For example: “We do not have enough money to pay for improvements to our railroads. And without improvements, this transportation system will falter and thus hinder our economy. Therefore, we should raise taxes to pay for better railroads.”
Pathos: appeals to the emotions of the audience
Such an appeal attempts to persuade by stirring the emotions of the audience and attempts to create any number of emotions, including: fear, sadness, contentment, joy, pride. Pathos does not concern the veracity of the argument, only its appeal.
Bob Dole wants to hurt the elderly by cutting Medicare.
Ethos: appeals exerted by the character of the writer/speaker
Such an appeal attempts to persuade by calling attention to the writer’s/speaker’s character. It says in effect: “I’m a great guy so you should believe what I’m telling you.” Ethos does not concern the veracity of the argument, only its appeal.
I am a husband, a father, and a taxpayer. I’ve served faithfully for 20 years on the school board. I deserve your vote for city council.