Famous examples of conceivability arguments include: (i) Descartes' argument for mind-body dualism; (ii) Kripke's 'modal argument' against psychophysical identity theory; (iii) Chalmers' 'zombie argument' against materialism; and (iv) modal versions of the ontological argument for theism. In this paper we show that for any such conceivability argument, C, there is a corresponding 'mirror argument', M. M is deductively valid and has a conclusion that contradicts C's conclusion. Hence a proponent of C-henceforth, a 'conceivabilist'-can be warranted in holding that C's premises are conjointly true only if she can find fault with one of M's premises. But M's premises-of which there are just two-are modeled on a pair of C's premises. The same reasoning that supports the latter supports the former. For this reason a conceivabilist can repudiate M's premises only on pain of severely undermining C's premises. We conclude on this basis that all conceivability arguments, including each of (i)-(iv), are fallacious.

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