Alexander Bird's talk last Wednesday
I enjoyed Alexander's talk last Wed, so I thought I'd try out the discussion feature of this blog with some comments about a side-issue that came up: his objections to the idea that objects are essentially members of the natural kind of which they are actually members. The idea is that a sample of gold is essentially gold; it can't cease to be gold without ceasing to exist, and that very same thing couldn't be anything other than gold.
We had some compelling examples to the contrary; the decay of Barium to Cesium for one. A sample of Barium changes very little when it becomes Cesium. It loses only a tiny part of its mass. Surely the thing still exists, it's just that it's now a member of a different kind.
This example and all the other ones were examples of something persisting but as a member of a different kind. One thought is that if you are a four-dimensionalist, a persisting thing is just a fusion of temporal parts -- so it's not obvious why it can't be a fusion of things that are themselves members of various kinds. The persistence criteria for objects are usually causal ones -- each later temporal part has to be caused in the right way by the earlier one -- and in all of Alex's examples, this was plausibly the case despite the earlier being a member of a different kind that the later.
But none of that, I think, bears on the question of whether the minimal entities -- the smallest temporal parts themselves -- are essentially members of the kind that they are members of. While, as a matter of fact, I don't think that they are, I think that a defender of that doctrine who is a four dimensionalist ought think that it applies only at the fundamental level. So a particular atom-temporal-part of Barium couldn't be the very same thing without being Barium (in nearby worlds where decay happened earlier that atom-slice doesn't exist, but a Cesium one does)
So I guess I think we need an independent argument for the modal claims as applied to the temporal parts.
3 comments:
Cool! When I have something to add I'll comment!
That's interesting. My first thought was that since lots of people think that synchronic composition is either a causal relation, or else supervenes on a (multigrade) causal relation, that we could use the same argument to conclude that in fact the only plausible candidate to be a member of a natural kind is the mereological simple.
If causation between temporal parts means its the smallest temporal parts, not the perduring whole that are the members of the NK, then by parity we should think its the smallest spatial parts not the composite, that are the members of the NK. That conclusion seems unlikely to appeal to most.
This in turn got me to wondering what the sense is, in which synchronic composition is supposed to involve causation. Is the implication that causation is not a cross-temporal relation? Or that in fact there are no instantaneous objects, but instead slightly temporally extended ones whose spatial parts are causally related in the appropriate manner?
It seems the main issue here is related to the fact that something with temporal parts can change - through time - to be a different kind of thing.
The thing which would seem to stop minimal temporal parts doing the same is that they are not extended along any dimension which permits change (in some relevant sense). So it's not as though these things are somehow more in touch with their essences - retaining them through thick and thin. They just don't go through any "thick and thin"!
I'm not suggesting anyone said otherwise, but it seems a useful point. It suggests that any objection ('independent argument') to the thesis that these things belong to their NK's essentially would have to come in the form of a counterfactual scenario where they differ as a whole, rather than a possibly-actual scenario in which they change from being one way to another.
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