Enthymeme

An enthymeme is a syllogism (a three-part deductive argument) with an unstated assumption which must be true for the premises to lead to the conclusion. In an enthymeme, part of the argument is missing because it is assumed.

Enthymeme's three parts

The following quotation is an example of an enthymeme.

"There is no law against composing music when one has no ideas whatsoever. The music of Wagner, therefore, is perfectly legal." —Mark Twain.

The three parts:

There is no law against composing music when one has no ideas whatsoever. (premise)

The music of Wagner, therefore, is perfectly legal. (conclusion)

Wagner has no ideas. (implicit premise)

More examples

First example: Socrates is mortal because he's human.

The complete syllogism would be the classic:

All humans are mortal. (major premise - assumed)

Socrates is human. (minor premise - stated)

Therefore, Socrates is mortal. (conclusion - stated)

Second example: "The glove doesn't fit defendant, so you must acquit."

The complete syllogism would be:

If evidence does not fit - acquittal is required (major premise - assumed)

The glove doesn't fit the defendant. (minor premise - stated)

Therefore, you must acquit the defendant. (conclusion - stated)

Stating the argument in this extended form suggests the argument is incomplete. For example, one might be more likely to ask if the glove might have shrunk or ask about the meaning of the expression the glove: What do you mean the glove?. The presence of the definite article the suggests that there is a definite descriptor phrase with the same meaning in this context. Examples of such phrases could be

The glove found at the scene of the crime
The glove used by the assailant.

For some definite descriptor phrases, the major premise of the above syllogism is clearly suspect.

(This argument is based on one used by Johnnie Cochran in his defense of O. J. Simpson.)

Hidden premises are often an effective way to obscure a questionable or fallacious premise in reasoning. Typically fallacies of presumption (fallacies based on mistaken assumptions, such as ad hominem or two wrongs make a right) are attracted to enthymeme.

Enthymeme use in humor

Enthymeme can be a humorous technique when the hidden premise is something surprising due to the context, its offensiveness or its absurdity.

Examples

"Senator, I served with Jack Kennedy. I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy." —Lloyd Bentsen to Dan Quayle, 1988. (The hidden premises might be, Jack Kennedy was a great man, and you are not a great man.)

"Now, I don't know or have never met my candidate; and for that reason I am more apt to say something good of him than anyone else." —Will Rogers. (The hidden premise is that once a person knows or meets the candidate they will not have as many good things to say about him.)

Use in advertising

Advertisers rarely draw out the links between the images they show and the product they wish to sell. There is no logical connection between a beautiful woman draped across the hood of a red sports car and the value of the car itself, but the advertiser implies a premise that there is. If the advertiser instead simply stated, "Buy this car and you will have more sexual satisfaction" it would be easier to reject as a premise.

To use another example, advertisers often show examples of people enjoying their product. They never actually state that the viewer should purchase the product or service that is bringing the people such enjoyment; it is an implied major premise.

Notes

Enthymemes are generally used for two reasons:

The implied premise is obvious
The implied premise is dubious

An example of the second reason would be, "Of course he is dumb, he is a man." The implied premise is "All men are dumb," which can easily be proven false by proving that one man is not "dumb," so the premise is left out in the hopes that the listener might not realize what was implied. When used in daily conversation, the implied premise is usually less obvious.

External links

Rhetoric

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