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Published online by Cambridge University Press: 13 August 2010
This paper presents a simple argument against life being the product of design. The argument rests on three points. (1) We can conceive of the debate in terms of likelihoods, in the technical sense – how probable the design hypothesis renders our evidence, versus how probable the competing Darwinian hypothesis renders that evidence. (2) God, as traditionally conceived, had many more options by which to bring about life as we observe it than were available to natural selection. That is, the relevant parameters were, in many cases, far more constrained under natural selection. (3) Utterly mundane features of the world, like that the earth is very old, are actually powerful evidence that the world was not designed, since that outcome was optional on the design hypothesis but nearly inevitable on natural selection.
1. It isn't discussed in major philosophical anthologies like Neil Manson (ed.) God and Design (New York NY: Routledge, 2003); or in compendia like Michael Martin Atheism: A Philosophical Justification (Philadelphia PA: Temple University Press, 1990); Richard Swinburne The Existence of God (Oxford: Oxford University Press, 2004); or in monographs like William Dembski The Design Inference (Cambridge: Cambridge University Press, 1998); Elliott Sober Evidence and Evolution (Cambridge: Cambridge University Press, 2008); or in popular digests like Jerry Coyne Why Evolution is True (New York NY: Viking, 2009); Richard Dawkins The Greatest Show on Earth (New York NY: Free Press 2009); or in official public summaries like the National Academy of Science Science, Evolution and Creationism (Washington DC: National Academies Press, 2008).
2. Ian Hacking The Logic of Statistical Inference (Cambridge: Cambridge University Press, 1965), 55ff.; John Leslie The End of the World (London: Routledge, 1996), ch. 5; Bradley, Darren & Fitelson, Branden ‘Monty Hall, doomsday, and confirmation’, Analysis, 63 (2003), 23–31CrossRefGoogle Scholar; Sober Evidence, ch.1.
3. Making stronger Bayesian assumptions, and assuming no other evidence is relevant, a simple calculation shows we should move from a prior probability on A's guilt of .5 – sheer uncertainty – to a relatively confident .67 with just the one extra car at B's disposal. Add a third and it's .75. Of course, I'm trying to avoid the stronger Bayesian assumptions throughout the paper; I mention this just to convey a sense of the significance of such evidence.
4. It isn't important to define ‘old’ as long we mean something like ‘at least tens of millions of years’, i.e. a period that is within the minimum natural selection might be thought to have taken, and that is still far greater than what God might have chosen.
5. It isn't important to attach precise values to either of these probabilities. We needn't assume P(E|H1) is 1 rather than, say, .9; and we needn't assume P(E|H2) is exactly .5, though it isn't clear what evidence would support a higher figure.
6. As before, we can illustrate the point in more robust Bayesian fashion. Suppose our prior probability on H1 is .5. (This isn't to make Laplacian indifference assumptions; we're just illustrating what would happen in a particular case, say with someone unmoved by other available evidence.) P(E|H1)= .9, say; let P(E|H2)= .5. For argument's sake, make the crude assumption that H1 and H2 are exhaustive, waiving life being seeded by aliens, wildly heterodox naturalistic theories, etc. Bayes' theorem says: P(H1|E)=P(H1)P(E|H1)/P(H1)P(E|H1)+P(H2)P(E|H2). And all this works out to.64, meaning that the simple point about the age of the earth should move our undecided individual to being reasonably confident that life is not the product of design, given these admittedly fraught assumptions, which the likelihood argument eschews.
7. See, e.g., Coyne Why Evolution, ch. 3.
8. On this assumption, see Bollingera, R., Barbasa, A., Busha, E. et al. ‘Biofilms in the large bowel suggest an apparent function of the human vermiform appendix’, Journal of Theoretical Biology, 249 (2007), 826–831CrossRefGoogle Scholar. On the second assumption, see Adams, Robert ‘Must God create the best?’, Philosophical Review, 81 (1972), 317–332CrossRefGoogle Scholar.
9. For more on these issues, see John Leslie Universes (London: Routledge, 1989), ch. 2; Michael Behe Darwin's Black Box (New York NY: Free Press, 2006); Liu, Renyi & Ochman, Howard, ‘Stepwise formation of the bacterial flagellar system’, PNAS, 104 (2007), 7116–7121CrossRefGoogle ScholarPubMed; S. J. Gould Wonderful Life (New York NY: W.W. Norton, 1990).
10. See, for instance, Neil Manson ‘The “Why design?” question’, in Y. Nagasawa & E. Wielenberg (eds) New Waves in Philosophy of Religion (New York NY: Palgrave MacMillan, 2008), and Alvin Plantinga ‘Epistemic probability and evil’, in Daniel Howard-Snyder (ed.) The Evidential Argument from Evil (Bloomington IN: Indiana University Press, 1996).
11. See Sober Evidence, sec. 2.12, for more detail on this point, including the issue of whether our evidence should be considered to be just the fact that humans have eyes, or the fact that humans have eyes with specific features F1…Fn.
12. I ignore the separate objection that anything God does has a probability of 1, because His actions are in some sense necessary. We could just as much object to attaching probabilities to the actions of criminal defendants, since they lie in the past. Presumably in these sorts of cases what we have in mind is evidential probability: we're interested in how likely it was that we'd observe an old earth, given that God designed life, in light of our evidence.
13. ‘Sitting calmly on a ship in fair weather is not a metaphor for having faith; but when the ship has sprung a leak, then enthusiastically to keep the ship afloat by pumping and not to seek the harbor – that is the metaphor for having faith’; Søren Kierkegaard Concluding Unscientific Postscript, Howard & Edna Hong (trans.) (Princeton NJ: Princeton University Press, 1992), 225fn.
