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An enthymeme (Greek: ἐνθύμημα, enthumēma), is an informally stated syllogism (a three-part deductive argument) with an unstated assumption that must be true for the premises to lead to the conclusion. In an enthymeme, part of the argument is missing because it is assumed.
Here is an example of an informal syllogism, an enthymeme:
While syllogisms lay out all of their premises and conclusion explicitly, enthymemes keep at least one of the premises or conclusion unsaid. The assertions left unsaid are intended to be so obvious as to not need stating.
Advice is given freely because so much of it is worthless.
Here, there is an explicit premise that advice is given freely. But an implicit premise is that all worthless things are given away freely.
Here is an example of a "a less-than-100% argument" stated by George Bernard Shaw:
Here there is an unstated premise that progress comes about when a man tries to adapt the world to himself. While all the premises are true, it is arguable that a man is "unreasonable" because he is trying to change the world.
Klamer et al. argue that Aristotle also addressed enthymemes as maxims:
"Aristotle noted that most arguments take the form of an 'enthymeme' ('EN-thu-miem'), an incomplete or not-quite-air-tight syllogism. 'Free trade is good' or 'Increased Taxes provide increased revenue' are enthymemes, not-syllogistic arguments. The average French economist may find such arguments 45 percent true, whereas the average American economist may find them 80 percent true. Arguing an enthymeme is successful when the economist defends the 45 or 80 percent true as 'true enough.' Economics, like other sciences, works in approximations."
In “Aristotle’s Rhetoric,” Christof Rapp discusses how Aristotle distinguishes between the two arguments, probably premises (eikos) and signs (semeia), that enthymemes are taken from. Aristotle says that enthymemes are based on probabilities, or tekemeria (proofs or evidence, and signs). Most people make rhetorical arguments by taking from probable premises.
“Arguments by sign assert that two or more things are so closely related that the presence or absence of one indicates the presence or absence of the other.” In “Aristotle’s Reasoning,” three different types are sign arguments are shown. Type (i) and (iii) are always refutable, even if the premises are true-meaning they don’t include a valid deduction (sullogismos). Aristotle calls them asullogistos (non-deductive). Sign argument type (ii) can never be refuted if the premise is true. Sign (ii) is also called tekmerion (proof, evidence).
|Look up enthymeme in Wiktionary, the free dictionary.|
|Wikisource has the text of the 1911 Encyclopædia Britannica article Enthymeme.|