Why are morphemes a useless concept? Has my entire linguistic undergrad experience lied to me???
Not if they believed it. If they believed it, then, of course, they weren’t lying. How could they be?
Anyway, for an answer vis-à-vis conlanging, see this post. I went over it there.
For linguistics, the reason you don’t use morphemes in analysis is it isn’t useful. If you have to hammer a nail into a wall, a hammer is a great tool. If you have to drill a hole in a wall, you probably shouldn’t use a hammer. Same thing if you want to screw in a screw. I mean, you could, but why would you when there are better tools?
Back to linguistics, the problem with (and benefit of) theories is that they hold generally. You can’t say, “Well, morphemes work great with Turkish—” (not true, but just for the sake of argument) “—but not so well with Arabic, so let’s use morphemes with Turkish and something else with Arabic!” No, no. Can’t do that. If the morpheme is a thing, it’s a thing everywhere. So you either decide to hold your nose and throw a bunch of zero morphs on forms that probably don’t need them, or you abandon the theory. (Or alter it in some way. No one seems keen on that.) I favor abandoning the theory, because once you do, you realize that it wasn’t really doing anything for you. You don’t lose anything. You still have affixes, roots, stems, etc., but you’re not stuck with having to explain that there are fifty different /-ī/ morphemes:
/-ī/ = nominative plural (masculine)
/-ī/ = vocative plural (masculine)
/-ī/ = genitive singular (masculine)
/-ī/ = genitive singular (neuter)
/-ī/ = vocative singular (masculine)
/-ī/ = dative singular (masculine)
/-ī/ = dative singular (feminine)
/-ī/ = dative singular (neuter)
/-ī/ = genitive singular (feminine)
/-ī/ = ablative singular (masculine)
/-ī/ = ablative singular (feminine)
/-ī/ = ablative singular (neuter)
/-ī/ = first person singular (perfect)
lol Like what even is a theory that has to list all this seriously?! And of course, it’ll all have extra information, like “This one is only used in X declension!” and it’s just…stahp. Like, no. Embarrassing. And the hilarious thing is that the similarity between all of these is incidental. Each one of those could, theoretically, have an entirely different phonological form, because by the theory, there’s no reason they shouldn’t. Sometimes that’s a good thing (often there are incidental similarities), but sometimes it isn’t—like those forms that have identical dative and ablative singular forms in all genders. Like, that’s no accident. But by the theory, it is. And that’s the thing that often gets swept under the rug. The theory is absolutely blind to phonological and semantic similarities between forms. It simply says “give me a word and I will divide it into pieces for you”.
The main thing, though, is once I left morphemes behind, my life (and conlanging) improved immeasurably. I miss nothing about that way of life.