I tire of hearing folks repeat “you cannot derive `ought’ from `is’,” because there is an important sense in which most attempts to derive “ought” are built on “is.” Let me explain.
An argument for an “ought” is typically built on some set of more basic “obvious” claims that the speaker assumes their audience will accept without argument. Many of those claims have their own supporting arguments somewhere else, but those arguments are also be built on further obvious claims.
Eventually we end up with with a set of basic supporting claims that seem obvious, but which don’t have much in the way of explicit arguments supporting them. Yes, almost always one of these obvious but not explicitly argued claims is of the “ought” type. So in this sense every “ought” is derived from other “oughts.”
However, a key implicit argument sits behind these obvious unargued supporting claims, namely that those claims seem right. That is, we typically assume that we should believe an “obvious” claim because our subconscious/intuition recommends that we believe such a claim.
Now in order for it to make sense to believe an “ought” claim that seems right to our intuition, we have to at least believe that our intuition tends on average to be right about similar sorts of claims. There is no point in believing our intuition on some topic if it has no consistent relation to the truth there.
But the claim that one’s intuition about a particular “ought” claim correlates with truth on that “ought” claim is itself an “is” claim. Yes that claim about the reliability of our intuition is itself also mainly supported by noting that this reliability claim seems right to our intuition, but I’m not complaining about that.
I’m instead pointing out that most every attempt to derive an “ought” is based ultimately on “is” claims about the reliability of our intuitions about such more basic “ought” claims. If we can’t find a coherent way to integrate these “is” claims with the rest of our network of reasonable “is” claims, then we can’t argue coherently for such “ought” claims at all.
(This same argument applies to “wow” claims on beauty; yes every “wow” claim appears derived from other unargued “wows” but the support for those “wows” are key “is” claims on the reliability of our “wow” intuitions.)
Nick, I'm not addressing Hume in the context of his writing, but the wider "you can't derive is from ought" claim tossed about casually as a very general and reliable theorem. Who actually proposed to or went to what effort to derive what when is not so relevant for evaluating the "you can't derive" claim. I'm not talking about efforts to derive or conscious intentions to derive; I'm talking about what people use to support their beliefs when those beliefs are called into question, besides just saying "because."
I'll follow your lead in elaborating the argument further, but renumber for clarity:1.(unexpanded) My meta seemings (about seemings) are reliable indicators of truths about seemings 2.(observation) My moral seemings seem (to me) reliable indicators of moral truth3 (combine 1&2) My moral seemings are reliable indicators of moral truth.4.(observation) It seems to me that harming innocents is wrong5.(combine 3&4) I know that harming innocents is wrong6.(unexpanded) If I know something, that something is true.7.(combine 5&6) Harming innocents is wrong.
My basic claim here is that all of the unexpanded and observation claims (1,2,4,6) are reasonably thought of as "is" claims.
The content of the belief that it seems to me that harming innocents is wrong includes the normative notion of wrongness. Therefore it could be argued that the proposition believed is normative (something similar to this issue was, if I remember rightly, discussed by Hare in his reply to Searle’s ‘How to derive an ought from an is’). You might reject this on the grounds that ‘seems’ is not a factive operator and so having a normative notion within its scope does not make the proposition normative. OK, so take it that both are purely descriptive beliefs. The derivation you are proposing is1.It seems to me that harming innocents is wrong2.My seemings seem to me to be reliable indicators of (moral) truth3.Therefore harming innocents is wrongI doubt whether I or anyone else actually derived their moral beliefs by such reasoning, any more than we reason from sensory seemings to perceptual beliefs. Rather, we have the sensory seemings and absent certain defeaters they cause us to have the perceptual belief, and this process is sometimes misleadingly described as an inference. Similarly my belief that harming innocents is wrong might be caused by it seeming like that.
But perhaps you are proposing that this is how an ethical intuitionist would defend the moral principle that harming innocents is wrong. There is a simple reason why no intuitionist should present this as a derivation of the moral principle: the form of the argument is invalid (and hence {1,2} is not a set of descriptive propositions that entail a normative proposition).
Some ethical intuitionists explain how it is that we know moral truth in terms similar to this (but the second premiss would be that seemings are reliable, not that seemings seem to be reliable). Taken like that, it is missing an intermediate conclusion ‘2b. therefore I know that harming innocents is wrong’. The step from 2b to 3 is valid but the argument as a whole is still invalid. Furthermore, such externalist explanations of knowledge are explanations of how we know what is true, when it is true, so properly formulated it would take 3 as a premiss, and 2b would be the conclusion.
Moreover, such explanations of moral knowledge don’t entail that belief in the conclusion (3) is not a basic belief, (in the sense that basic beliefs are where the regress of justification stops). For example, if intuitionists were then to explain the seeming and the reliability in terms of conceptual competence and the nature of the concepts involved their whole story could be that ‘harming innocents is wrong’ is a self evident proposition.
Finally, you might say, great, the step from 2b to 3 shows that you can derive an ‘ought’ from an ‘is’, since 2b is prima facie a descriptive proposition whilst 3 is normative. First of all, that’s fine, since I was not trying to defend Hume’s critique but point out that it was about entailment of normative propositions rather than knowledge of them. Secondly, however, since knowledge is factive it is less clear that it is a mere quibble to point out that the proposition ‘I know that harming innocents is wrong’ contains a normative notion. The normative notion is within the scope of a factive operator and that looks like a ground for saying it is a normative proposition. Thirdly, setting that aside, 2b is still the wrong kind of proposition to embarrass Hume’s critique. He is criticising people for deriving things like ‘you ought to help Fred’ from ‘Fred is suffering’ alone. That you can derive ‘you ought to help Fred’ from ‘I know you ought to help Fred’ is beside his point.