another way to be contrary

(cross-posted from the Dublin Philosophy Blog)

I posted a while ago with a list of the different ways I thought one could object to an argument; roughly, accept the form by deny a premise, accept the premises by deny the conclusion follows from those premises, or accept the conclusion, the form and the premises, but dismiss it as unimportant, or question begging.

Well, I came across an interesting variation on the first approach today. One says the premises are in tension with each other, in that believing one premise undermines one’s grounds for believing one of the others. That is to say, one challenges the advocate’s right to jointly assert the premises as opposed to challenging the premises’ joint truth.

This mode of objection is a bit like the third of my first three ways, in that it pertains not to the substance of the argument but to the pragmatics of argument. As far as the substance of an argument is concerned, the argument is sound as soon as the argument is valid and the premises are all true. However, in debate, what matters are one’s attitudes to the premises and to the validity. Ignorance of the truth of the premises is almost as great an obstacle to accepting the conclusion as knowledge of the falsity of the premises. This modification challenges the argument by challenging its pragmatic credentials. It alleges that the argument could never be convincing, because no one could have the right attitude to the premises. One could never legitimately believe them all. The argument therefore fails because it would be irrational to believe the conclusion on the basis of the argument.

This suggests there is an analogous modification to the second of my first three ways. This would be to deny anyone could ever be in a position to know that the argument is valid, and hence to deny that anyone could legitimately believe the conclusion on that basis. I guess something like this underlies worries about the status of computer proofs in mathematics.

The example I came across was Geoffrey Sampson’s response to Stephen Stich and associated reply in the British Journal for the Philosophy of Science.
Geoffrey Sampson “Popperian Language-Acquisition Undefeated” The British Journal for the Philosophy of Science Vol. 31, No. 1, Mar., 1980 (pp. 63-67) Stable URL:
Stephen Stich “Cn Popperians Learn to Talk?” The British Journal for the Philosophy of Science Vol 32, No.2, (1981): 157-76. Stable URL:


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