Name of assertions in sentences where negation of the whole sentence doesn't negate the assertion

Question

A few years back I watched a talk by a German linguistics professor where he (IIRC) mentioned a rhetorical technique where the writer of a speech moves certain facts into a secondary position in a sentence, in which the assertion stays as is even if the sentence is negated.

Sadly, I don't remember the exact talk, but I wondered if there is a name for that. Here are two examples:

Everyone knew that he lied about the reasons for war.

There are multiple "assertions" made in this sentence. First that "everyone knew" and second that "he lied". Now if you ask someone to negate that sentence, I think most people would say: "Not everyone knew that he lied about the reasons for war". So most people would only negate the first assertion.

Another example would be:

He felt as exhausted as many working class people feel every day.

Probable negation: "He didn't feel as exhausted as many working class people feel every day", leaving the assertion that working class people that way every day untouched.

Is there a name for those type of assertions or a name for the technique of asserting things in this by-the-way style?

Answer 1

Technically speaking, these are not assertions. The technical term is presupposition.

Assertions are propositions that one can negate, like

• The moon is made of green cheese.

whose negation is

• The moon is not made of green cheese.

Presuppositions, on the other hand, are propositions that can't be negated so easily. They are occasioned by many different words ("lexical items") or constructions, which are said to "license" the presupposition.

Predicates are of many different semantic types, and predicates like know, discover, and be aware of that license a presupposed complement clause are known as factive predicates:

• He doesn't know that the Earth goes around the Sun.
• Galileo discovered that Jupiter has satellites.
• Were you aware that there is an earlier train?

The boldfaced propositions above are presupposed to be true, whether the sentence is negated or not. Factive predicates are only one variety of presupposition triggers.

Answer 2

What you are looking for is presupposition:

Sentence A presupposes sentence B iff both A entails B and the negation of A entails B.

An alternative definition is that

A presupposition is a proposition such that the speaker acts as if that proposition was true/as if that proposition is taken for granted, i.e. already known.

By wrapping the "he lied" sentence into "everyone knew", the speaker presupposed that he lied. It is not possible to directly negate this embedded sentence by negating the matrix clause, and the speakers acts as if the proposition "he lied" is taken for granted.

Negating the sentence and checking whether the proposition still follows is one way to test for presupposition. Another test is to make it a question: "Did everyone know he lied?" still entails that he lied.

The so-called factive verb "to know" is what triggers the presupposition. Other triggers include change of state verbs ("he stopped lying"), certain adverbs ("he lied again"), particles ("... and she lied, too") and some more.

The "... as ..." construction is an interesting example that I haven't seen cited in the context of presupposition before, but thinking about it, it has all the typical properties of a presupposition. Nice find you made!