The Language of Argument

9 7

su p p r e s s e d P r e m i s e s

Traditionally, logicians have called premises that are not stated but

are needed (to make the argument valid and explain how it works) sup-

pressed premises. An argument depending on suppressed premises is called

an enthymeme and is said to be enthymematic. If we look at arguments that

occur in daily life, we discover that they are, almost without exception, en-

thymematic. Therefore, to trace the pathway between premises and conclu-

sion, it is usually necessary to fill in these suppressed premises that serve as

links between the stated premises and the conclusion.

Contingent Facts

Suppressed premises come in several varieties. They often concern facts or

conventions that might have been otherwise—that are contingent rather

than necessary. Our example assumed that the dead are not eligible for the

presidency, but we can imagine a society in which the deceased are elected

to public office as an honor (something like posthumous induction into the

Baseball Hall of Fame). Our national government is not like that, however,

and this is something that most Americans know. This makes it odd to come

right out and say that the deceased cannot hold public office. In most set-

tings, this would involve a violation of the conversational rule of Quantity,

because it says more than needs to be said.

Even though it would be odd to state it, this fact plays a central role in

the argument. To assert the conclusion without believing the suppressed

premise would involve a violation of the conversational rule of Quality, be-

cause the speaker would not have adequate reasons for the conclusion. Fur-

thermore, if this suppressed premise were not believed to be true, then to

give the explicit premise as a reason for the conclusion would violate the

conversational rule of Relevance (just as it would be irrelevant to point out

that Babe Ruth is dead when someone asks whether he is in the Baseball

Hall of Fame). For these reasons, anyone who gives the original argument

conversationally implies a commitment to the suppressed premise.

Suppressed premises are not always so obvious. A somewhat more com-

plicated example is this:

Arnold Schwarzenegger cannot become president of the United States,

because he was born in Austria.

Why should being from Austria disqualify someone from being president?

It seems odd that the Founding Fathers should have something against that

particular part of the world. The answer is that the argument depends on a

more general suppressed premise:

Only a natural-born U.S. citizen may become president of the United

States.

It is this provision of the U.S. Constitution that lies at the heart of the ar-

gument. Knowing this provision is, of course, a more specialized piece of

knowledge than knowing that you have to be alive to be president. For this

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