What is conversational IMPLICATURE? ⟨09,03⟩

Описание: When we use conditionals in natural language like English, what are we saying? This is actually an astonishingly difficult question, which has received a ton of attention in the secondary literature.

Nobody agrees on much, but there is a general agreement that there's a meaningful distinction to be drawn between what a conditional LOGICALLY implies from what it CONVERSATIONALLY implies. For example, suppose I tell you "I'll go to the picnic unless it rains". We know from an earlier video ⟨09,01⟩ that this is equivalent with "If it doesn't rain, I'll go to the picnic". Now suppose it rains, but I show up to the picnic anyway. Was my original claim false?

In fact, it wasn't. Notice that a conditional is only false if it goes from T to F. But if the latter half of the conditional is true ("I'll go to the picnic"), then the whole thing comes out true.

One impulse is just to say we're reading conditionals wrong. Another is to say that "If it does rain, I won't go to the picnic" isn't part of what the conditional LOGICALLY implies, but merely what it CONVERSATIONALLY implies. So we're tempted to read a simple conditional (~P→Q) as a much stronger biconditional (~P↔Q). But that's not part of its original content.

How do we determine what the original content is? CANCELABILITY. If you suspect something is a conversational but not a logical implicature of a sentence, try negating it, and see if that cancels the original claim. So for our picnic example, we could say, "I'll go to the picnic unless it rains...And in fact I'll go even if it does rain". There's no contradiction here. So the implication that I won't go to the picnic if it does rain is not part of the logical content of the original statement.