As I said in my previous post, there’s a lot wrong with Robert Pennock’s piece ”Can’t Philosophers Tell the Difference Between Science and Religion? Demarcation Revisited”, in the new edition of But is it Science?. Here is just one of the problems. 

Pennock is famous (or perhaps infamous) for holding that claims about supernatural beings are untestable; Pennock says that the supernatural is inherently mysterious to us. I have a lot to say about why that’s wrong in my forthcoming book, Seeking God in Science: An Atheist Defends Intelligent Design. Elliott Sober also has a nice argument that some some claims about supernatural beings are testable. Sober gives the example:

the claim that an omnipotent supernatural being wanted above all that everything in nature be purple.

This is a claim that’s testable — we can observe the world, see that not everything is purple, and conclude that the claim is false. But Pennock takes issue with this. He writes:

Might not all of nature now indeed “be purple” in its noumenal substance, irrespective of its accidents, as wine purportedly becomes blood without observable change in the miracle of the Eucharist? (p. 552)

Pennock concludes that Sober’s claim is not testable.

But Pennock’s reasoning is misleading here. There are two ways to understand the thesis that a claim is testable. One way, the weak way, is to hold that one can get powerful evidence for or against the claim. The other way , the strong way, is to hold that one can get conclusive proof for or against the claim. Now, If one understands testability the strong way, then it turns out that virtually no scientific claim is testable — we don’t have conclusive proof  that we’re not brains in vats, and hence however the world appears to us via our scientific investigation could be false, because it could be the case that we’re brains in vats and the real world containing the vats is different from how the world appears to us. So the strong way is unreasonable. On the weaker way, then ordinary scientific claims are testable, even though we can’t get conclusive proof for or against them, just as the claim that everything in nature is purple is testable, even though we can’t get conclusive proof against that claim. Thus, on a reasonable understanding of what it is for a claim to be testable, Sober has provided a good example of a claim about the supernatural that’s testable.

Here’s another way to respond to Pennock. We could just change Sober’s example slightly, so that we’re talking about 

the claim that an omnipotent supernatural being wanted above all that everything in nature APPEARS TO US TO BE purple.

This claim is testable, even on the strong reading of testability. It follows that Pennock is wrong to hold that claims about the supernatural are not testable.

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