When we speak, we end up carrying out whole cascades of meaning and connections to other sentences that go beyond the specific truth of what we actually said. And these meanings come in a few varieties. Implicatures are inferences about what someone meant to say, based on the idea that they're trying to be a cooperative conversation partner. And by cooperative, we mean that they're following the Cooperative Principle, and follows the four Conversational Maxims we talked about before. Implicatures aren't required by logic to be true, and so an implicature can be false even when the underlying statement remains true, a feature known as cancellability.
Entailments are propositions that are 100% guaranteed to be true, if the original sentence that's said is also true. That can be because of knowledge about the world, two synonymous words, or because if something is a member of a smaller group, it must be a member of a larger one, etc. Unlike implicatures, entailments aren't cancellable: if the statement is true, whatever entailments it produces must also be true.
Finally, presuppositions are statements that are just assumed as background information for the sentence that you're saying. If you have a presupposition in your sentence, it just has to be true, or the sentence can't really be interpreted. It's not that if the presupposition is false, the sentence is false; it's that if the presupposition is false, the whole sentence can't be either true or false. It's just... there. Presuppositions can get introduced into sentences by some adverbs like again, some verbs like admit, and some embedded sentences.
Linguists have spent a lot of time exploring the ways in which what we say carries information over to a listener — ways that go above and beyond the mere words in a sentence. And as it turns out, whether a sentence implicates, entails, or presupposes another isn’t random; instead, there are some interesting patterns lurking about. Let's look at a couple of places where presuppositions like to hang out.
One class of words that seem to regularly introduce presuppositions into sentences is verbs, but we can be a bit more discriminating than a simple syntactic category. One important subclass of verbs that predictably trigger a presupposition is factive verbs. These words, like “admit” and “regret”, can only be used appropriately if what follows them can be taken for granted as true; after all, it would be hard to regret something that didn’t even happen. Let’s have a look at one of these in context:
(1) Holmes admitted that he cared for Mrs. Hudson
Notice that this sentence wouldn’t make very much sense if Holmes didn’t like Mrs. Hudson in the first place. Using a factive verb means that a speaker (or writer) has taken for granted that the sentence that follows the verb — its complement — is true, and assumes that the hearer (or reader) does so too. This collective pool of knowledge that’s shared between speakers is the common ground. And we can be sure this is the case, since if we extend the sentence to negate what’s taken for granted, we get a contradiction. This is to be expected, as you might recall from the episode that presuppositions are unlike implicatures in that they cannot be cancelled.
(2) Holmes admitted that he cared for Mrs. Hudson, but he didn’t care for her.
Other sorts of verbs that trigger presuppositions include aspectual verbs (e.g., “continue”, “finish”), which roughly speaking communicate whether some action or state is currently taking place, has already happened, or is just about to begin; desiderative verbs (e.g., “want”, “wish”), which denote desires and which presuppose the negation of their complements, since if you still desire something, you don't have it yet; iterative verbs (e.g., “return”, “reconsider”), which indicate repetition, since you can't do something again if you haven't done it at least once already; and the class of implicative verbs (e.g., “manage”, “remember”), which behave a lot like the factive verbs described above, but have complements beginning with the infinitival marker “to” instead of the complementizer “that”. Take a look at the following examples, to get a sense of how these work in a sentence; in each case, the first sentence in a pair presupposes the second.
(3) Holmes continued to investigate the crime.
(4) Holmes investigated the crime.
(5) Magnussen wanted to blackmail Mary.
(6) Magnussen had not blackmailed Mary.
(7) Holmes returned to England.
(8) Holmes had once been in England.
(9) Moriarty managed to fool everyone.
(10) Moriarty fooled everyone.
Now, you might think that once a presupposition finds its way into a sentence, it’s there for good. After all, we know that even if you negate a sentence, the presupposition remains. Negation is what’s known as a hole, since it allows a presupposition to pass freely from a lower subordinate clause into a higher one. Both (11) and (12) presuppose (13).
(11) Holmes suspected others knew that Watson had been in the military.
(12) Holmes didn’t suspect others knew that Watson had been in the military.
(13) Watson has been in the military.
But there exist filters (e.g., “and”, “if . . . .then”) and plugs (e.g., “promise”, “accuse”) as well, which either selectively filter out certain presuppositions or block their transmission altogether, respectively. In (14), the presupposition found in the if-clause — that Mary has a secret past — applies to the sentence as a whole. But, if we switch things around a little, the story changes; in (15), the then-clause presupposes that Mary has a secret past, yet the sentence as a whole does not. Conditional statements like those below can be choosy about which presuppositions are allowed to stick around.
(14) If Watson knew that Mary had a secret past, then Mary would worry.
(15) If Mary has a secret past, then Watson knows it.
And while it’s plain that the sentence in (16) presupposes that Mrs. Hudson had prepared afternoon tea, (17) could just be an empty promise.
(16) Mrs. Hudson had finished preparing afternoon tea.
(17) Mrs. Hudson promised Watson that she had finished preparing afternoon tea.
From the facts above, we can see that like the tight-knit relationship between meaning and syntactic structure, presuppositions are also governed by rules which appear to regulate where they can and cannot stick around, in addition to the rules that determine whether they can show up to begin with. And all this is just a small taste of the research that’s been done!
So how about it? What do you all think? Let us know below, and we’ll be happy to talk with you about all the different ways that we enrich meanings beyond what we actually say out loud. There’s a lot of interesting stuff to say, and we want to hear what interests you!