Why none of us quite know what we're talking about

Photo by Douglas English (circa 1902) / Flickr

It would be hard to find an adult native speaker of English who was anything less than absolutely certain that they knew the meaning of the word mouse. It is, after all, a word that is perfectly at home in children's storybooks, and certainly nothing anyone would ever think of as a difficult technical term. About as many native speaking adults would also feel the same about the word rat, but not all of them could say with confidence how exactly a mouse differs from a rat, or apply their implicit understanding of what these words mean to distinguish say, a juvenile rat from an adult mouse. The average person knows a lot of things about these animals but not necessarily enough to tell them apart in every single case.

There's a whole genre of commonly confused animal terms in English with which we could make a similar observation: monkey vs. ape, alligator vs. crocodile, turtle vs. tortoise, rabbit vs. hare, frog vs. toad, crow vs. raven, and so on. Many of us struggle with at least some of these distinctions, or if not these particular examples, then others. In such cases, it's safe to say that our mental representations of the meanings of the words involved are not completely fleshed out despite whatever confidence we may have that we know what each of these words means individually. Of course, if our dinner depended on being able to tell various animal species apart, we'd probably do far better, but unless a distinction is relevant for something, we usually content ourselves with the thought that the details are known to somebody somewhere and that we could easily look them up if necessary.