Abstract
I first support Alec Fisher's thesis that premises and conclusions in arguments can be unasserted first by arguing in its favor that only it preserves our intuition that it is at least possible that two arguments share the same premises and the same conclusion although not everything that is asserted in the one is also asserted in the other and second by answering two objections that might be raised against it. I then draw from Professor Fisher's thesis the consequence that in suppositional arguments the falsity (or unacceptability) of a supposition does not tell unfavorably in the evaluation of the argument, because the falsity (or unacceptability) of a (nonredundant) premise counts against an argument if and only if that premise is asserted. Finally, I observe that, despite the fact that they are neither expressed nor even alluded to, implicit assumptions in arguments are always asserted, unless the conclusion, but none of the explicit premisses, is unasserted. Hence, apart from an exceptional case of the kind just mentioned, the falsity (or unacceptability) of implicit assumptions always counts against an argument.
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I am indebted to Thomas E. Gilbert and Alec Fisher for their criticisms of an earlier draft of this paper.
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Bowles, G. Professor Fisher on suppositions. Argumentation 7, 237–246 (1993). https://doi.org/10.1007/BF00710810
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DOI: https://doi.org/10.1007/BF00710810