Inchoate = Not Choate? Only by Accident . . .
On page 15 of his book What We See When We Read (Vintage Original, 2014), Peter Mendelsund says:
You may feel intimately acquainted with a character . . . , but this doesn't mean you are actually picturing a person. Nothing so fixed - nothing so choate.Mendelsund may well be correct that we don't picture a character as we read, but what does he mean by "choate"? Does he consider it the opposite of "inchoate"? This word (as we all know) means: "2. Imperfectly formed or developed; disordered or incoherent" (The Free Dictionary by Farlex). That would suggest "choate" means "Perfectly formed or developed; ordered or coherent."
But "in-" in this usage does not mean "not"; rather, it is the enceptive "in-," which signals the beginning of a process. By a stroke of linguistic luck, then, something is inchoate because the process has only begun, so the thing is still in a disordered state, not yet choate, i.e., ordered - just as if "-in" meant "not"!
But is "choate" actually a word? There is some dispute about this, but "choate" has been used as a legal term since 1828, according to Wikipedia, and it means "perfected, complete, or certain" in a legal context.
Whether Mendelsund knew all of this or not, then, he could justifiably defend his choice of the term "choate" since its legal meaning fits the context here . . . insofar as we are judging character.