Subject: [evol-psych] "ought" can be plausibly derived from an "is"?
   Date: Wed, 20 Feb 2002 00:02:19 -0800
   From: "Pascal Bercker" 

David Hill writes: 

>  That an "ought" can be plausibly derived from an "is" can be
> established as follows.  From (1) my knife is dull, it can be
> plausibly derived that (2) my knife ought to be sharpened, given the
> assumptions that (3) knives are for cutting and (4)sharp knives cut
> better than dull ones. 

> Caveats:  (i) these implications are not logical entailments;

This caveat is absolutely central, and it remains that an "ought" has 
*not* been derived from an "is" in any straightforward sense of 
"derive". As Hume suggests, your going from purely *descriptive* 
premises to a *prescriptive* conclusion about what "ought" to be done 
involves a wholly new relation, the logic of which needs explaining. 

IF an implicit premise is also the claim, for example, that one *ought* 
to restore lost function to things (the knife having lost its function by 
becoming dull) then you do simply have a derivation of an "ought" 
from a more general "ought", which nobody contests is possible. What 
is contestable, of course, is the alleged truth of the implicit prescriptive 
premise, or presumably any general premise like it. You seem to 
recognize this when you say: 

> I suppose this could be elicited as a fundamental normative claim
> without which the conclusion will not follow, but surely this is a
> point of no practical importance. 

But your claim that it's a point of no practical importance simply misses 
the central *philosophically* important point that we wish to know what 
reasonable (or evidential) support we can give even to *fundamental 
normative* claims, given that any derivation from purely *descriptive* 
factual premises is simply not on. 

This takes on practical importance we there is genuine disagreement 
over what these fundamental normative claims are supposed to be, 
and how they are to be ranked in degree of importance when they 
come into conflict, and so on. 


Pascal Bercker