One of Jerry Fodor’s arguments against reductivism in his 1974 paper is that bridge laws reducing, say, economics to physics are undermined by the possibility of simulations of economic systems that instantiate the same economic ‘laws’ but have a very different physical basis from economic systems that are composed of interacting humans. It’s difficult to imagine what bridge laws would carry out the reduction successfully for both the simulated economy and the real human economy.
Someone in class pointed out that this would seem to be more of a problem for economics than for something like chemistry. After all, it seems like the physical basis for chemical systems has to be electrons, protons, and so on — the ontology of quantum mechanics, the science to which it allegedly reduces. What other physical basis could there be?
But then there are such things as simulations of chemical systems. If we take these to be parallel to the case with simulated economic systems, then bridge laws relating chemistry to quantum mechanics would have to cover not only the cases where the physical properties are instantiated in an actual physical system, but also those where they aren’t actually instantiated but represented in a computer simulation.
I take it that it would be an unacceptable move to say that the laws of chemistry don’t apply to simulated chemical systems, and in any case it’s difficult to see why one should be allowed to say that and not allowed to say that the laws of economics don’t apply to economic systems that aren’t composed of humans.
The only other way at present I can think of to get out of this bind is to say we should somehow regard the chemical simulation as instantiating the physical properties it represents. But the awkwardness in that phrase (what does it matter how we regard it — it either instantiates them or it doesn’t, regardless of our regard) suggests that I can’t find a way to make this sound like a good move. And in any case we run into the same problem: why should we do this for the chemistry case but not for the economics case?
Still, I have this intuition that somehow chemistry is essentially about actual atoms and molecules, while economics is more removed from the material nature of the systems it is applied to. But I can’t think of a way to justify it.
Posted by Ponder Stibbons 
