What makes something grammatical?
Someone called E has posted a question in the comments section of my last post—The VanDamme Academy, and why grammar is not about clarity—Part 2. I was going to answer it there itself, but I realized this had enough material to be a post, so here it goes.
First, his question:
So, what, according to you, is ‘unconditionally ungrammatical’ about _They is walking_? If it conveys all the information the speaker intends to convey, unambiguously, the only thing wrong with it is the fact that it does not follow convention (the convention of conjugating a verb a certain way with certain subjects)