Swinburne Evolved

Posted on November 28, 2008

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We had Richard Swinburne in town on Wed, offering an interesting seminar paper, the stated thesis of which was ‘it is impossible to offer scientific explanation of the evolution of humanity’ – he did pause to reassure us that he is very happy with a (neo-)Darwinian account of evolution by natural selection, &c., to account for speciation. So why the problem?

The basic argument relied on a particular take on the philosophy of science. We may usefully divide properties/events into ‘physical’ and ‘mental’, according to Swinburne, and science necessarily deals with only physical properties/events. (He defined an event as ‘a substance having a particular property at a particular time’.) However, what it is to be human (and, by supposition, a member of various species of the higher animals) involves a series of mental events/properties, and so is necessarily opaque to science.

A ‘mental’ event/property is one to which ‘the substance in whom it is instantiated necessarily has privileged access’ (quoted from Swinburne’s handout). This gets us into a hard mind/brain distinction: the chemical state of my brain is a physical event: I have no direct access to it, and anyone can in principle investigate it. However, my feeling interest, excitement, or fear, is a mental event: no-one else has access to those feelings. Of course, it is almost certainly the case that many – perhaps all – mental properties either cause or are caused by certain physical properties, but they remain different events. I can know that I feel fear without knowing anything about my brain chemistry; you can know something about my brain chemistry without knowing anything about how I am feeling.

The essence of science is repeatable observation; this is, by definition, impossible, for mental properties and events. Science is remarkably successful at investigating the physical world, but does so often precisely by replacing language of mental events (‘heat’), which is necessarily opaque, with language of physical events (the random motion of particles, or electromagnetic radiation) which is susceptible to scientific investigation. Therefore, if it is of the essence of being human to be possessed of certain mental properties, there is no available scientific account of what it is to be human, or of how humanity appeared on earth. Swinburne suggested five such properties: the possession of mental properties simpliciter; the occurrence of intentional events; the two-way interaction between mental events and brain events; the possession of moral beliefs; and the possession of libertarian free-will (which he acknowledged to be contested).

This is all very neat, and difficult to criticise as a piece of logic. What of the premises? It seems to me that the crucial assumption is that only I am able to observe my own mental processes. Presuming that the universe is less hospitable to telepaths than many of our sci-fi novelists have imagined (which seems to me a reasonable presumption), this assumption is still, it seems to me, straightforwardly false. God knows me better than I know myself, and this would seem to include my mental properties.

I suspect that the argument could be re-written to take account of this point: God is, after all, not your average scientist (I will resist any of the obvious rude comments…). If my criticism stands, then two potentially interesting results follow. The first is that Swinburne’s assumption of libertarian free will becomes decisive for his argument. If I am possessed of libertarian free will, then there might in principle be aspects of my mental life to which God has less immediate access than I do (which seems to me another in a long list of fairly devestating arguments against libertarian free will, but…). Second, Swinburne’s argument could be taken as a demonstration that it is impossible to believe in evolution if one happens to be an atheist, which would be a pleasing conclusion to be able to demonstrate in the present cultural climate…

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