Philosophy Bites interviews philosopher Helen Beebee on The Laws of Nature and Beebee continually revisits the metaphor of a fragile glass throughout the interview as she builds this poetic line of thought:
When you say a glass is fragile, you’re saying something about how it’s going to behave in certain kinds of situations. If I say, “Oh be careful that glass is fragile,” you know that I’m telling you not to drop it on the floor, or to dry it very carefully, or whatever it is, because to be fragile is to be disposed to break in certain kinds of situations.
[…What] the defender of the Armstrongian, Necessitarian view is going to say is: look, fragility isn’t really a fundamental property. What underlies the fragility of the glass is the fact that the glass has a certain kind of microstructure. And it’s a law of nature that things that have that kind of microstructure shatter when they come into contact with hard surfaces.
But just the fact that that glass has that microstructure and the floor is hard just by itself, that doesn’t guarantee anything about how the glass is going to behave. You could imagine a world where glass with the same kind of microstructure got dropped on hard floors and nothing bad happened, the glass just kind of bounced up. The laws of nature would have to be different, but that’s perfectly conceivable.
So in the Armstrongian view, we have to now think there’s a necessary connection between what’s happening with the microstructure of the glass when it comes into contact with a very hard surface. That’s an extra fact, as it were, about the relationship between those two things.
Now, the Dispositionist Essentialist view agrees on the case of fragility because they don’t think that fragility is a fundamental property, but let’s imagine that fragility is a fundamental property. The thought is that the very fact that the glass is fragile, the fact that that’s a disposition to break in certain kinds of circumstances, once you know that the glass has that disposition, you know that the glass is going to break. A fragile glass couldn’t help but break. Try to imagine an impossible world now where you have a fragile glass that doesn’t break when you drop it on a hard surface. You can’t do it, unless you imagine it being encased in bubble wrap or something. In exactly the same circumstances, if the glass is fragile, it’s guaranteed to break so you don’t need that extra, as it were, necessary connection to tie those two things together. It’s just given by the fact that the glass has that property, that it must break.
