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.

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, so you must acquit."

The complete syllogism would be:

• If the glove doesn't fit the defendant, you must acquit the defendant. (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 that 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.

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.)

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

"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. The beautiful women, draped across the dashing red sports car... there is no logical connection between the two, but the advertiser would like to imply a premise that there is. If the advertiser came out and said "Buy this car and you will have more sexual satisfaction" it might be easier to reject as a premise.

To use another example, advertisers often show examples of people enjoying their product. They never actually say "... and, you should do what these people do," it is an implied major premise.

External links

• Extensive bibliography of enthymeme in scholarly literature