Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Some call the enthymeme a rhetorical syllogism, while others regard it as a part of the syllogism, because whereas the latter always has its premises and conclusion and effects its proof by the employment of all its parts, the ethymeme is content to let its proof be understood without explicit statement.
The following is an example of a syllogism:
Virtue is the only thing that is good, for that alone is good which no one can put to a bad use: but no one can make a bad use of virtue; virtue therefore is good.The enthymeme draws its conclusion from denial of consequents.
Virtue is a good thing because no one can put it to a bad use.On the other hand take the following syllogism.
Money is not a good thing; for that is not good which can be put to a bad use: money may be put to a bad use; therefore money is not a good thing.The enthymeme draws its conclusion from incompatibles.
Can money be a good thing when it is possible to put it to a bad use?
The following argument is couched in syllogistic form:
If money in the form of silver coin is silver, the man who bequeathed all his silver to a legatee, includes all money in the form of coined silver: but he bequeathed all his silver: therefore he included in the bequest all money in the form of coined silver.But for the orator it will be sufficient to say,
Since he bequeathed all his silver, he included in his bequest all his silver money.