The Asymmetry Thesis

Abstract

In a series of articles1 Gerald Massey has defended asymmetry the thesis that the present stage of logical theory our ability to prove validity totally eclipses our ability to show invalidity.2 My initial strategy in discussing this thesis will be to close in on it gradually by con sidering, sometimes summarily but sometimes in greater detail, various distinguishable theses in the neighborhood, gradually approximating the thesis which Massey wishes to defend. For starters, the thesis is an epistemological one and certainly does not involve any claim to the effect that there is no adequate account of what the distinction between valid and invalid arguments is. In accepting what he calls the Principle of Logical Form (Arguments that instantiate valid argu ment forms are valid) and, albeit somewhat less enthusiastically, its con verse (Valid arguments instantiate valid argument forms),3 Massey evidently endorses something like the following account of the distinction: an argument is valid if and only if it instantiates a validating form.4 Once the distinction between arguments and forms is broached, it becomes important to emphasize that Masseyan scepticism about invalidity concerns arguments rather than forms; he has no evident scruples, for ex ample, about instancing affirming the consequent as not being a validating form.5 So the thesis is an epistemological thesis, a thesis about what we can know, and a thesis about arguments rather than forms. Distinctions still need to be made, however. Massey has no evident objection to saying on the basis of that various egregiously bad arguments are bad.6 Evidently he would not, or at least he need not, object to the claim that our intuition that the following argument is invalid amounts to knowledge that it is: