But, in all seriousness, how does one "inhabit" a number on a character sheet? The character I'm interested in inhabiting is not the character sheet. It's a fiction in my imagination.
Sure, but if the fiction in my imagination is a brilliant self-assured nimble wizard who is now and then somewhat clumsy - and that's what I'm roleplaying - yet the sheet says St 16, In 9, Wi 8, Dx 16, Co 12, Ch 7, I'd say that anyone would be quite justified in telling me I'm outright doing it wrong and I'd have no defense whatsoever.
Before you inhabit the house you have to build it; and if the building materials you have are wood then you can't use them to make a brick house no matter how hard you try. The best you can do is carefully paint the wood so it looks like brick.
Well, the analogy here is that all those things on the character sheet are your building materials.
I'm trying to imagine how this works, but I've got nothing.
Player writes LG on character sheet. Player has character consistently act neither L nor G at such times when it's advantageous to do so. When called on it either in the fiction or at the table, player's (somewhat meta) defense is "Go ahead, cast
Know Alignment - I'm Lawful Good. It says so right here!"
I saw this once too often back in the day, and thenceforth have made it very clear that while you can write an alignment on the sheet it might not hold up if you don't then at least vaguely play to it.
See, this is where I think it's useful to have something written on the character sheet, because there are mechanics with which it interacts. I have mechanics that interact with alignment in my game, and I want my players to be aware of those mechanics and how they affect resolution, so the alignment on the sheet is the one being used for that.
Where I make it very clear that the alignment those mechanics are going to see is what's arisen out of how the character has actually been played, unless the character is brand new and hasn't established any patterns yet.
I was talking about the idea of incentive, though. There are real incentives for strong people to use their superior strength just as there are real incentives for smart people to use their superior intelligence. But how is an unintelligent person incentivized to have fewer ideas or insights?
They're not. They're just incapable of having more, no matter what incentives are put in front of them. And when you say stats don't matter it kinda comes across as a desire, in this example, to ignore or brush off this incapability and have the character instead be able to come up with all the ideas and insights it wants to (i.e. you're playing to your intelligence, not the character's).