Maiya busted me yesterday on multiple-digit numbers. They do not take an apostrophe, as do single-digit numbers when plural, so my post needed editing to incorporate her correction. I had already edited it once to add in the its/it’s confusion, my original motivation for writing about apostrophes in the first place.
To recap that one little area: its: possessive pronoun (like my); it’s: it is. They are not interchangeable. This is not a question of variable style on which opinions may differ.
My crank for today is short and simple. I, he, she, they are subject pronouns. The object forms are me, him, her, them. (You doesn’t change so creates no problems.) The most common error made by educated people is to use ‘I’ when ‘me’ is correct. “They gave Richard and I a gift.” No, no, no!!! You would never say, “They gave I a gift,” would you? Correct: “They gave Richard and me a gift” or “They gave a gift to Richard and me.” When in doubt, leave the proper name out and see how it sounds.
John O’Hara used the incorrect form intentionally in dialogue, arguing with copy editors who wanted to "correct" the way his characters spoke that young, upperclass, educated people really did make this mistake all the time. And such people--not just young ones, either--still do. So if you’re writing dialogue, and you want to show your character making a grammatical error, it works. Otherwise, you’re the one making the error, and that doesn’t work.
Oops, I almost forgot the joke. It’s about a philosopher giving a lecture and looking to generalize his point by using letters instead of specific object names. He was talking about 'essences,' or what medieval philosophers called ‘quiddity,’ such as the 'horseness' of horses, only he didn’t want it to sound as if only horses or apples or tables had essences, so he began by using the letters ‘a’ and ‘b’ but was quickly led into a –ness form that sounded very peculiar and distracting. Backtracking, he erased the chalk letters ‘a’ and ‘b’ on the board and replaced them with the letters ‘p’ and ‘q’. Where the lecture went from there I leave to your imagination.
Yes (sigh!), this is what passes for a joke among philosophers.