[MD] Putnam on Is-Ought and Truth

[Horse]

On 28/04/2010 22:28, Steven Peterson wrote:
> Hi Craig,
>
> On Wed, Apr 28, 2010 at 2:53 PM,<craigerb at comcast.net>  wrote:
>    
>>
>> [Craig, previously]
>> [P1] Socrates is a man.
>> [P2] A man is mortal.
>> [C1] :.Socrates is mortal.
>>
>> [Steve]
>>      
>>> What is implicit and agreed upon in advance without needing to be
>>> stated is a premise P3 that tells us that such premises like P1 and P2
>>> when taken together ought to make us conclude the sorts of claim that
>>> you have concluded. Without such an additional ought-premise your
>>> conclusion would be unwarranted.
>>>        
>> You're confusing inference rules with premises.
>> Antidote @
>> http://www.ditext.com/carroll/tortoise.html
>>
>>
>> The inference rule states that if each premise IS true, then the conclusion
>> also IS true.  What you ought to conclude is an additional question.
>>      
>
> What you ought to conclude is what the inference rules are
> prescribing. Aren't rules sorts of "oughts"? What is a rule if not a
> claim about what ought to be done under certain circumstances? In
> other words, I don't think I'm confusing them. I think such rules
> really ARE premises that are taken for granted with out stating them
> as such. Rules are norms and "oughts" that must be presupposed to be
> able to derive an is from other ises. I think this is what Horse was
> saying earlier.
>
>    
There are two ways of looking at this. No new "is" is being created 
really as you are just substituting one example with another (using the 
ISA rule):

Socrates isa [Man]
A [Man] isa Mortal

By substitution

Socrates isa Mortal

another way of looking at it in the slightly expanded form that Craig 
suggests would be

If [it is true that]
Socrates is a man
And If [it is true that]
A man is Mortal
then
Socrates ought to be mortal

The tricky bit with this sort of logic (and why I've substituted ought 
for is) is whether all men are mortal, as the complete set of men, past 
present and future, of which man is an instance, has to be assumed!
Ah, the fun you can have with logic!!

Horse
-- 

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but to skid in sideways, chocolate in one hand, wine in the other, body thoroughly used up, totally worn out and screaming "WOO HOO what a ride!"... Hunter S Thompson