en·thy·meme /ˈɛnθəˌmim/

–noun Logic.
a syllogism or other argument in which a premise or the conclusion is unexpressed.

1580–90; < L enthȳmēma < Gk enthȳ́mēma thought, argument, equiv. to enthȳmē-, var. s. of enthȳmeîsthai to ponder ( en– en-2 + –thȳmeîsthai v. deriv. of thȳmós spirit, thought) + –ma n. suffix of result

—Related forms
en·thy·me·mat·ic  /ˌɛnθəmiˈmætɪk/, adjective

Source: Dictionary.com.

“The Devil (God save us!) does not tempt a monk with serpents and two-headed men. If anything, with lascivious visions, as he tempted the fathers in the desert. And besides, if it is evil to handle certain books, why would the Devil distract a monk from committing evil?”

“That seems to me a good enthymeme,” my master admitted.

Source: The Name of the Rose by Umberto Eco.