“Can” is the opposite of “unable”. “Unable” means that the change involves granting ability to they who would act, i.e. teaching a technique, providing a tool, fixing the body, or altering the environment.
That’s a good characterization, though arguably not a definition, as it relies on “ability”, which is circular. I can do something = I have the ability to do something. I can = I’m able to.
But we can use the initial principle (it really needs a name) which doesn’t mention ability:
You do a thing iff you can do it and you want to do it.
“Iff” behaves similar to an equation, so we can solve for “can”, similar to algebra in arithmetic. I don’t know the exact algebra of “iff”, but solving for “can” arguably yields:
“I can do X” iff “If I wanted to do X, I would do X”
Which uses wanting and a counterfactual to define “can”. We could also define:
“I want to do X” iff “If I could to do X, I would do X”
Though those two definitions together are circular. Maybe it is better to regard one concept as more basic than the other, and only define the less basic one in terms of the more basic one. It seems to me that “want” is more basic than “can”, so I would only define “can” in terms of “want”, and leave the definition for “want” open (for now).
2
Regarding the Confusing Cases. There are at least two canonical classes: akrasia (weakness of will) and addiction. “Can” the addict quit smoking? “Can” the person suffering from akrasia just do The Thing?
A better question perhaps: In which sense is the answer to the above “yes” and in which sense is it “no”?
One possibility is to analyze these cases in terms of first-order vs second-order desires. The first-order desire would be smoking or being lazy, the second order desire would be not to have the (first-order) desire to smoke, or be lazy. Second-order desires seem to be more important or rational than the first order desires. The second-order and first-order desire are “inconsistent” here. If the first-order desire to smoke is stronger than the second-order desire not to have the first-order desire, I don’t quit smoking. (Or don’t overcome my laziness in case of akrasia). Otherwise I do.
Here, the “can” definition as “If I wanted to do X, I would do X” is ambiguous. If it means “If I had the first-order desire to quit smoking, I would quit smoking”, then the sentence is true, and I “can” overcome the addiction (or the akrasia). If it means “If I had a second-order desire to not have the first order desire to smoke, I would quit smoking”, then the sentence is false, as I do in fact have the second-order desire but still don’t quit. So in this sense it’s not true that I “can” quit.
A similar but different different analysis wouldn’t phrase it in terms of first and second-order desires, but in terms of rational wishes and a-rational urges. I wish to quit smoking, but I have the urge to smoke. I wish to get to work, but I have the urge to be lazy. If we count, in the definition of “can”, urges as “wanting”, I can stop smoking, if we count “wishes” as “wanting”, I can’t. By a similar argument as above.
I think these cases are actually not a major problem of the “can” definition. After all, it seems in fact ambiguous to ask whether someone “can” overcome some case of akrasia or addiction. The definition captures that ambiguity.
That’s some careful analysis!
Two remarks:
1
That’s a good characterization, though arguably not a definition, as it relies on “ability”, which is circular. I can do something = I have the ability to do something. I can = I’m able to.
But we can use the initial principle (it really needs a name) which doesn’t mention ability:
“Iff” behaves similar to an equation, so we can solve for “can”, similar to algebra in arithmetic. I don’t know the exact algebra of “iff”, but solving for “can” arguably yields:
Which uses wanting and a counterfactual to define “can”. We could also define:
Though those two definitions together are circular. Maybe it is better to regard one concept as more basic than the other, and only define the less basic one in terms of the more basic one. It seems to me that “want” is more basic than “can”, so I would only define “can” in terms of “want”, and leave the definition for “want” open (for now).
2
Regarding the Confusing Cases. There are at least two canonical classes: akrasia (weakness of will) and addiction. “Can” the addict quit smoking? “Can” the person suffering from akrasia just do The Thing?
A better question perhaps: In which sense is the answer to the above “yes” and in which sense is it “no”?
One possibility is to analyze these cases in terms of first-order vs second-order desires. The first-order desire would be smoking or being lazy, the second order desire would be not to have the (first-order) desire to smoke, or be lazy. Second-order desires seem to be more important or rational than the first order desires. The second-order and first-order desire are “inconsistent” here. If the first-order desire to smoke is stronger than the second-order desire not to have the first-order desire, I don’t quit smoking. (Or don’t overcome my laziness in case of akrasia). Otherwise I do.
Here, the “can” definition as “If I wanted to do X, I would do X” is ambiguous. If it means “If I had the first-order desire to quit smoking, I would quit smoking”, then the sentence is true, and I “can” overcome the addiction (or the akrasia). If it means “If I had a second-order desire to not have the first order desire to smoke, I would quit smoking”, then the sentence is false, as I do in fact have the second-order desire but still don’t quit. So in this sense it’s not true that I “can” quit.
A similar but different different analysis wouldn’t phrase it in terms of first and second-order desires, but in terms of rational wishes and a-rational urges. I wish to quit smoking, but I have the urge to smoke. I wish to get to work, but I have the urge to be lazy. If we count, in the definition of “can”, urges as “wanting”, I can stop smoking, if we count “wishes” as “wanting”, I can’t. By a similar argument as above.
I think these cases are actually not a major problem of the “can” definition. After all, it seems in fact ambiguous to ask whether someone “can” overcome some case of akrasia or addiction. The definition captures that ambiguity.