## Tuesday, December 15, 2020

### A proof that ought implies can

Some actions are are things I can do immediately: for instance, I can immediately raise my hand. Others require that I do something to enable myself to do the action: for instance, to teach in person, I have to go to the classroom, or to feed my children, I need to obtain food. So, here is a very plausible axiom of deontic logic:

1. If I ought to do A, and A is not an action I can do immediately, then I ought to bring it about that I can immediately do A.

Now, say that I remotely can do an action provided that I can immediately do it, or I can immediately bring it about that I can immediately do it, or I can immediately bring it about that I can immediately bring it about that I can immediately do it, or ….

It follows from (1) and a bit of reasoning that:

1. If I ought to do A, then I remotely can do A, or I have an infinite regress of prerequisite obligations.

But:

1. It is false that I have an infinite regress of prerequisite obligations.

So:

1. If I ought to do A, then I remotely can do A.

Michael Gonzalez said...

What about the third option in which I can remotely bring it about that someone or something else can remotely/immediately do A? I don't see why the chain has to end up in myself doing A immediately.

Alexander R Pruss said...

If I can remotely bring it about that I can remotely bring it about that I can do A, then it seems that I can remotely bring it about that I can do A.

Michael Gonzalez said...

Yes, but I'm asking about a case in which I remotely bring it about that you or someone else -- or perhaps some machine or something else -- does A. Your definition of "remotely doing A" makes it seem like the chain can only include links in which I immediately do a thing leading to another thing that I immediately do, etc. Why can't it be that I need to do things which eventually lead to someone else or something else doing A?

Alexander R Pruss said...

Sure, but I am interested in what follows from "I ought to do A". And it doesn't follow--at least not as a matter of deontic logic--that *you* ought to make me be able to do A.

Helen Watt said...

Slightly separate issue but there's surely some doubt that ought always implies can?

I ought to do X immediately (it's an emergency) but wrongly believe X is immoral and can't disabuse myself in the next second. God could give me special knowledge but let's imagine that's not going to happen. I ought not to do X-in-bad-faith, and I also ought not to do non-X-in-good-faith since my view about the immorality of X is simply mistaken.

Everyone able to act in that situation ought to do X immediately, in good faith, and that includes me. However, X immediately in good faith is not something I'm psychologically able to do.

Alexander R Pruss said...

Helen:

I am inclined to think "I should do X in good faith" is probably shorthand for something other than the paradigm moral action-guiding should. It could be shorthand for: I am morally defective insofar as I do not do X in good faith. Or maybe: I should have gotten myself to the point where I could do X in good faith and then should have done it.

I think we do have such uses of "should". For instance, suppose that I promised to be in a meeting across town at 9 am. It's now 8:55 am and I have just woken up. "I should be driving to the meeting now" sounds correct, but of course I can't, and this "should" is not the paradigm action-guiding should. It's something like: "I should have so acted as to be driving to the meeting now."

Helen Watt said...

Alex:

Maybe though I inherited a faulty alarm-clock - i.e. I'm naturally slow in thinking about moral questions (not very bright or with little intuition) and/or facing some thorny dilemma (new biological technology?) where even bright intuitive virtuous people could well get it wrong especially if they have only a second to choose. Can't you still say, I should have done X meaning just, X was the right choice unbeknownst to me? That's what we'd say with a hard mathematical problem.

Alexander R Pruss said...

Maybe we want to distinguish what the intellect should do from what the will should do. If the will goes for the best of the options presented by the intellect, the will has done what it should.

Helen Watt said...

I see what you mean but isn't there something lacking in a moral-information-deprived will? It's not meant to operate that way any more than the mind and brain are meant to record the bizarre input of a diseased eye. And as regards the virtues you might have the virtue of conscientiousness but be hampered in other virtues even if you don't have the corresponding vice exactly.

David Gordon said...
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David Gordon said...

Doesn't step 2 beg the question? Someone who denies that ought implies can claims that there is at least one thing that you ought to do but are not able to do, either immediately or by a series of steps. On this view, step 2 is an incomplete disjunction and one should add to it "or there is no series of steps that will get you in a position to do A immediately." In that case, denying that you are under an infinite regress of prerequisite obligations doesn't entail that you can do A remotely. You may not be able to do it at all, if it's not the case that ought implies can.

Alexander R Pruss said...

Since Step 2 is a logical consequence of Step 1, it can't beg the question.

David Gordon said...

Then the problem, I think, is in Step 1. If it is modified to "If I ought to do A, and A is not an action I can do immediately, and there is a series of steps that culminates in my being able to do A immediately, then I ought to bring it about that I can immediately do A," the infinite regress of prerequisite obligations is avoided.

Alexander R Pruss said...

I don't find the modification plausible. It seems that I ought always to put myself in the position of being able to fulfill my obligations.

Pascal88 said...
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Pascal88 said...
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Pascal88 said...
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Pascal88 said...
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Alexander R Pruss said...

Premise P3 seems false, even if one accepts the energy theory in the parenthesis of P1. If I asked Clark Kent for something, I thereby asked Superman for it, even if I don't know that Clark Kent is Superman. Similarly, if God is identical to all the energies, if I pray to God, I pray to all the energies.