Monday, October 26, 2009

Is/ought revisited

Here is a reputedly defensible version of the famous principle that you can't derive an 'ought' from an 'is', taken from a paper in defense of the principle that 'ought' implies 'can' (Peter B. M. Vranas, 2005) (this was linked by ephphatha in a previous post), although the link is now broken:

(I/O) No valid argument has a conclusion that is a singular* moral claim and premises that form a consistent set of nonmoral claims.

My question is, does the following example serve as a counter-example to I/O? (Also, if so, why? If not, why not?):

1) Jones believes that Smith ought to concede that we can derive an 'ought' from an 'is'.
2) Everything that Jones believes is true.
3) Smith ought to concede that we can derive an 'ought' from an 'is'. (from 1 and 2)

*singular moral claims are understood as moral claims expressed by asserting or denying that a specific agent S has (or does not have) a moral obligation to @.

3 comments:

Sam said...

Hmm. That's a good question. I would probably use a different example, though. The "ought" in your argument looks more like a rational ought than a moral ought. You could say:

1. Everything Jones says is true.
2. Jones says that it's morally wrong to lie.
3. Therefore, it's morally wrong to lie.

My initial reaction is to think something is awry, but I'm not sure what. How about this? Although the conclusion follows from the premises, this is not really a case of an ought coming from an is. The reason is because Jones saying something or believing it is not what MAKES the conclusion true. It was true already. All this argument does is give us a way to RECOGNIZE that the conclusion is true. So the argument confuses ontology and epistemology. The is/ought principle is an ontological principle.

But this does raise an interesting question for me as a moral objectivist who believes that morals are grounded in the character of God. It seems to be part of my worldview that morality exists because things are a certain way. Since there *is* a God who's character causes him to condemn stealing, stealing is therefore morally wrong. The ought appears to follow ontologically from the is in my worldview. I'm gonna have to think about this.

Psiomniac said...

Thanks for taking the time to give a considered response, I appreciate it.
I take the point on the rational ought.

My initial reaction was that something was awry too, but the two ideas that occurred to me were different to yours, which is interesting. I'll have to think about your ontology/epistemology distinction.

What occurred to me was that 1 (in your version) might covertly violate the consistency clause in I/O. In other words, without knowing the complete set of beliefs (or sayings in your version) how do we know that 1 is even self-consistent? However I rejected that, since although you might think there is a Gödel-incompleteness option here, I rejected this approach, reasoning that Jones might believe (or say) a minimal set of things that could be shown to be consistent.

The next thing that seemed awry to me was that in order for Jones to only say true things, this entails that everything Jones says must be truth-apt. But if we concede in one of the premises that moral statements are truth apt, then the argument is viciously circular.

But I'm not happy with either of these.

My initial reaction to your ontological/epistemological distinction is logic doesn't really care about causal relations, only inferential ones. So if your argument is valid, it is a counter-example to I/O, even if Jones has not caused 3.

Hmm..

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