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Posts Tagged ‘Realism-AntiRealism debate’

Are Evolutionary Debunking Arguments really self-defeating?

In Philosophy of Biology, Sterpetti on March 25, 2013 at 4:07 PM

Recently Helen De Cruz and her co-authors supported the view that Evolutionary Debunking Arguments (EDAs) (Kahane 2011) are self-defeating. Their argument can be summarized as follows: if human knowledge is not reliable since human reasoning is not truth-tracking, then even evolutionary theory, being a product of human reasoning, is not reliable; given that “EDAs themselves are based on scientific theories, notably evolutionary theory, and philosophical reflection” (De Cruz et al. 2011, p. 525), then EDAs themselves are not reliable, nor truth-tracking, and so are self-defeating.

            This objection to EDAs is similar to Reuben Hersh’s objection to the claim that, by Gödel’s second incompleteness theorem, the purpose of mathematical logic to give a secure foundation for mathematics cannot be achieved, and then mathematics cannot be said to be absolutely certain (Cellucci 2013, § 1.6). The response given by Carlo Cellucci to Hersh’s objection shows that such claim about mathematics is not self-defeating, and can be adopted to show that EDAs are not self-defeating as well.

            Hersh’s objection runs as follows: “If mathematics cannot be said to be absolutely certain, then Gödel’s second incompleteness theorem, being a mathematical result, cannot be said to be absolutely certain. But the claim that mathematics cannot be said to be absolutely certain is based on Gödel’s result. Then this claim too cannot be said to be absolutely certain. Therefore, the claim that, by Gödel’s second incompleteness theorem, mathematics cannot be said to be absolutely certain is self-defeating” (Ibidem).

            To face Hersh’s objection, Cellucci has argued that: “this objection is unjustified, because the argument that, by Gödel’s second incompleteness theorem, mathematics cannot be said to be absolutely certain, does not depend on the assumption that Gödel’s second incompleteness theorem can be said to be absolutely certain. It is a reduction to the impossible, because it is of the following kind. Let us suppose, for argument’s sake, that mathematics can be said to be absolutely certain. Then Gödel’s second incompleteness theorem, being a mathematical result, can be said to be absolutely certain. But, by Gödel’s second incompleteness theorem, mathematics cannot be said to be absolutely certain. Thus mathematics cannot be said to be absolutely certain. Contradiction. Therefore mathematics cannot be said to be absolutely certain” (Ibidem).

            So, it is possible to restate De Cruz’s objection (o) and propose a Cellucci-style response (r) to such objection, as follows: (o) if human scientific reasoning cannot be said to be truth-tracking, then EDAs, being based on human scientific reasoning, cannot be said to be truth-tracking. But the claim that human scientific reasoning cannot be said to be truth-tracking is based on EDAs. Then this claim too cannot be said to be truth-tracking. Therefore, the claim that, by EDAs, human scientific reasoning cannot be said to be truth-tracking is self-defeating; (r) this objection is unjustified, because the argument that, by EDAs, human scientific reasoning cannot be said to be truth-tracking does not depend on the assumption that EDAs can be said to be truth-tracking. It is a reduction to the impossible, because it is of the following kind. Let us suppose, for argument’s sake, that scientific reasoning can be said to be truth-tracking. Then evolutionary theory can be said to be truth-tracking. Then EDAs, being based on evolutionary theory, can be said to be truth-tracking. But, by EDAs, human scientific reasoning cannot be said to be truth-tracking. Thus evolutionary theory cannot be said to be truth-tracking. Contradiction. Therefore human scientific reasoning cannot be said to be truth-tracking.

            So, since adopting the argument described above the claim that, by EDAs, human scientific reasoning cannot be said to be truth-tracking can be shown not to be a self-defeating claim, then such argument shows that EDAs are not self-defeating arguments.

Fabio Sterpetti

Bibliography

Cellucci, C. (2013): Rethinking Logic. Logic in Relation to Mathematics, Evolution, and Method, Dordrecht, Springer.

De Cruz, H.; Boudry, M.; De Smedt, J.; Blancke, S. (2011): Evolutionary Approaches to Epistemic Justification, Dialectica, vol. 65, no. 4, pp. 517-535.

Kahane, G. (2011): Evolutionary Debunking Arguments, Noûs, vol. 45, no. 1, pp. 103-125.