The Logic of 'I Can'

While Descartes focuses on the Logic of 'I doubt', his effort is complicated by his seeming unawareness of the complications of the Logic of 'I can doubt'. More precisely, it is the Logic of 'I can' that is the source of the complication. For, the semantics and truth conditions of 'I can X', i. e. what it means, and its relations to some state of affairs to which it presumably refers, seem to elude the operations of traditional declarative Logic. In some respects, the meaning of 'I can X' resembles that of 'A causes B', namely, that it often entails 'I have done X', with no new accomplishment sufficing to satisfy 'I can X'. But, even without skepticism about its causality, the performance of X only proves that 'I have X', or even 'I was able to X', but not 'I can X', even in an isolated case. For, say that the performance begins at t, and is complete at u--at t, 'I can X' has not been proven, and at u, only 'I was able to X' has been proven. In other words, even if one does perform X, there is no time at which 'I can X' is true. Falsification is no less unwieldy, though it does assist in better defining 'I can X'. At t, 'I cannot X' is indeterminate, nor does the failure at u do have performed X suffice to falsify 'I can X', but the latter does show that 'I can X' entails 'I attempt X'. So, 'I can X' seems definable as 'If I attempt X, I accomplish X'. Still, establishment of the truth conditions of the latter seems to remain difficult, since it entails accurately determining at what point effort qualifies as 'attempt', i. e. not trying hard enough does not mean not being able. So, independent of the Logic of doubting, the logical status of 'I cannot doubt that I can (or do) doubt' is problematic for Descartes.