"Andrew O’Hagan writes: ‘Joan Didion gave me her hand and she was so thin it felt like I was holding a butterfly’ (LRB, 7 November). A beautiful sentence, but I wondered about the simile’s plausibility. It’s been reported that Didion weighs less than eighty lbs. She’s so thin her doctors have put her on an ice cream diet to keep her mass up. A woman’s hand is said to be 0.5 per cent of her body weight. So if Didion weighs 75 lbs, her hand probably weighs about six ounces. The world’s heaviest butterfly, the female Queen Victoria Birdwing, weighs about two grams. There are about 28 grams in an ounce, and Joan Didion’s hand probably weighs about the same as holding 86 female Queen Victoria Birdwings..."
[from a letter to the London Review of Books].
Well, I think the guy coming up with the simile knew that a human hand does not literally weigh as much as a butterfly. The simile is plausible because that was the mental image he got when he shook her hand.
This made me think. I'm trying to push for the idea that you should at least consider the literal level of the metaphor before you just try to forget about it. Performance, for example, is often used just as a metaphor for all kind of notions of authenticity and spontaneity. You can't study performance in an of itself, because the reason you are studying it has to do with these positive human values you want to tie it to.