Moral Theory and the Ought—Can Principle

Abstract

Does 'ought' imply 'can'? Surely it does. For we do not hold a person to blame for not doing something he was unable to do.' On the other hand, surely it does not. For, if it did, the negation of a 'can'-statement would imply the negation of an 'ought'statement. And thus descriptive statements of the form 'A cannot do x' would imply normative statements of the form 'It is not the case that A ought to do x', in violation of Hume's law that descriptive statements do not imply normative statements.2 It looks, then, as though neither a negative answer (for the former reason) nor an affirmative answer (for the latter one)to our question is satisfactory. Let us try to find a way out of this antinomy. I begin by considering the latter part of the antinomy. A key point here is that, since 'ought' implies 'can', it follows that 'not-can' implies 'not-ought'. Now it might be argued that the difficulty is an illusory one, on the ground that