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2/02/2005

Are humans part of nature?

In an earlier post, I took issue with Max Goss's claim that humans were not part of the natural world. He had said:

I have been reflecting a bit myself on man's responsibility to animals and the broader natural world. (This latter locution already tips my hand by suggesting that I consider animals to belong wholly to the natural world, whereas I consider humans to belong to it only in part.)

and

I don’t see any logical incompatibility between the claim that animals have rights and the claim that conservatism is true. But there might at least be a tension there, at least insofar as conservatism involves a commitment to what I call "minimal humanism," i.e. the belief that human beings are importantly distinguished from the rest of the natural world.

I responded:
I don't quite understand exactly what it means to say that animals are wholly natural, but humans are only partly so. What, exactly, is the distinction being made here? How is "natural" defined in such a way as to exclude (or even more bizarrely, partly exclude) human beings? What is it about humans that make them separate from nature? Of course, it's obvious enough that humans are a very different type of animal, in that they exhibit a number of unique characteristics -- language, abstract reasoning, etc. But on the standard view, this is simply a result of the human species having taken a different evolutionary path than other species have. It's not clear that there's a need to suppose a separate ontological category to account for the differences between humans and other animals.

In response to this, David from E.G. commented:

One way to read Max's claim is just as a denial of certain versions of physicalism, e.g. reductive versions. Such a denial is certainly not unusual among contemporary philosophers and remains a live option.

David is right that many philosophers do, in fact, reject reductive physicalism, which is (roughly) the claim that all existing entities either are themselves microphysical entities or that they are explainable in terms of their constituent microphysical entities (e.g., the way that (according to some) chemistry reduces to physics).

In fact, in my opinion physicalism is a hopeless cause. Every formulation I have ever seen of it is either incoherent or trivial. The main difficulties seem to be (a) offering a workable definition of the physical and (b) supporting the claim that "higher-level" phenomena (e.g., weather patterns) are somehow reducible to "lower-level" principles (physics).

(a) is a problem because no matter how one defines "physical", there are seemingly fatal problems. If it is defined in terms of current physics--that is, the physical is that which is described by physics--then physicalism is almost certainly wrong, since no one believes that physics is totally complete and totally correct. Otherwise, research in physics would cease immediately.

If "physical" is defined over a future, complete physics, then the physicalist claim becomes trivial, saying, in essence, "the only things that exist are those things which exist". By stipulating that a future physics would be complete, one begs the question in favor of physicalism. A future complete physics would by definition encompass everything.

There have been attempts to define the physical in terms of certain characteristics, but most are unworkable. For instance, Descartes defined it as that which is located in space. In light of special relativity, we might want to ammend that by saying that the physical is the spatio-temporal. However, this is unlikely to work as well, given (a) the possibility that not everything described or referenced by physics is spatio-temporal (e.g., the wavefunction) and (b) the possibility that space and time are actually emergent properties of more basic entities.

One exception is the definition of the physical given by, among others, Bertrand Russell and David Chalmers, who define it as those characteristics of nature which can be fully specified in terms of structure and dynamics. This definition won't work for the physicalist, though, as the qualitative character of experience--i.e., conscious/subjective experience--is clearly incapable of being captured in structural and dynamical terms.

So basically, physicalism is dead in the water, as Nietzsche saw over a century ago.

What's important, though, is that a rejection of physicalism not be seen as a rejection of what Chomsky calls "methodological naturalism", by which he means something akin to a scientific worldview, albeit one not based on the metaphor of the universe as a vast machine. The failure of physicalism in no way entails the success of any particular supernatural or religious metaphysics. Such theories might be true, but they will have to gain acceptance on their own merits, and not piggyback on the failure of physicalism.

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