Why is there a distinction between "it's" and "its"?
You can write "The cat's walking." where "cat's" might ambiguously be either "cat is" or "cat (possessive)", and I don't think anyone considers this to be a major problem of usage. What's different with its/it's?
Perhaps it is better to compare with other pronouns.
Its is substantially different in form than other genitive pronouns, in that it appears to be a relatively modern construction (OED has the earliest attested use in the 15th century) which in fact generalizes from the apostrophe possessive, or is a result of the same transformation that produced the apostrophe from OE strong|singular|masc./neut. -es. "Him"->"his" definitely isn't generalized from a widely attested grammatical rule; they've been in the language from old english essentially unchanged. By the logic that "its" operates similarly to other pronouns one would expect its (its' ?) modern form to be something like "his" which was its' original genitive form.
So my question is, who decided that its doesn't get an apostrophe, and why?
