ought implies can.

Kant famously asserted that if you ought to F (e.g. keep a promise or help a friend) then you can F—i.e., that ought implies can.  Like much of what Kant said, he probably didn’t mean what he said. (Perhaps more charitably: Kant didn’t mean what we—the uninitiated—think he means by what he said.)  For this reason, I don’t wish to discuss whatever Kant means by “ought implies can”. Instead, I wish to discuss the principle that ought implies can.  Here are four putative counterexamples to such a principle; the first three are counterexamples ex rationis exempla, the last is ex Scriptura.

Counterexample 1, 2, and 3

Suppose that Rex, without Jane’s consent, injects Jane with heroin. Suppose further that Jane’s brain chemistry is such that she becomes an addict and proceeds to act like one.  It seems to me that Jane ought not act like an addict.  Yet, it seems that Jane cannot help but behave like an addict.  Therefore, the principle that ought implies can is false.

Suppose that for years Ronald suffered abuse from his parents.  As a result, Ronald is emotionally unavailable to his wife.  It seems to me that Ronald ought to be emotionally available to his wife.  Yet it also seems that Ronald could not have been emotionally available to his wife.  Therefore, the principle that ought implies can is false.

Suppose that Michael suffers from social anxiety and, as a result, he often lets his friends down. It seems to me that Michael ought not let his friends down.  But, it also seems that, at least in some cases, Michael is constitutionally unable to not let his friends down.   Therefore, the principle that ought implies can is false.

Counterexample 4

The Holy One commands us to “[b]e perfect…” (Mat. 5:48).  Because we ought to do what the Holy One commands us to do, it follows that we ought to be perfect.  But, as the record of human history and the heap of anyone’s own personal anecdotal experience should suggest, our human condition is such that we are constitutionally incapable of being perfect.  Therefore, the principle that ought implies can is false.

A Better Principle

Because Holy Writ and our own personal experience, in addition to my first three counterexamples, show that the principle that ought implies can is false, I wish to supplant it with a better one. Here's the Better Principle: if S ought to F, and S will be morally responsible for her F-ing, then S can F.