Re: Solidity is degree of justification (was: Mirror neurons at autopsy)

On 26 Dec 2012, at 22:07, David Deutsch <david.deutsch-LR/[email protected]> wrote:

> On 26 Dec 2012, at 19:55, Alan Forrester <[email protected]> wrote:
>> 
>> On 26 Dec 2012, at 19:30, David Deutsch <david.deutsch-LR/[email protected]> wrote:
>> 
>>> On 26 Dec 2012, at 19:23, Alan Forrester <[email protected]> wrote:
>>> 
>>>> On 26 Dec 2012, at 13:42, David Deutsch <david.deutsch-LR/[email protected]> wrote:
>>>> 
>>>>> On 26 Dec 2012, at 04:08, therealjoshjordan <[email protected]> wrote:
>>>>> 
>>>>>> --- In [email protected], David Deutsch <david.deutsch@...> wrote:
>>>>>>> 
>>>>>>> In [email protected], Elliot Temple <curi@> wrote:
>>>>>>> 
>>>>>>>> On Dec 18, 2012, at 2:53 PM, David Deutsch <david.deutsch@> wrote:
>>>>>>>> 
>>>>>>>>> (Well, I say we know this -- but that explanation is not nearly as solid as the ones above.
>>>>>>>> 
>>>>>>>> This is justificationism.
>>>>>>> 
>>>>>>> I don't think it's a good idea to extend the meaning of the term 'justificationism' in this way, to include claims that more is known about one subject than another. 
>>>>>> 
>>>>>> In chapter 15 of Boi (p 352), David wrote:
>>>>>> 
>>>>>> "[...] rational thinking does not consist of weighing the justifications of rival theories, but of using conjecture and criticism to seek the best explanation [...]" 
>>>>>> 
>>>>>> Leaving aside for now the proper definition of the term "justificationism", how is judging theories by degrees of solidity any different from "weighing the justifications of rival theories"?
>>>>> 
>>>>> For instance, in the case where this 'judging' is about whether our best explanation about one issue is better than our best explanation about another issue, those two explanations are not rival theories, and hence the claim has nothing to do with weighing the justifications of rival theories.
>>>> 
>>>> No judgements of this kind are necessary.If two theories have no problems for which they both have implications then no comparison between them is necessary. If they do both have implications for the same problem then the comparison is done with respect to the issue for which they both have implications. This view of solidity still seems to be justificationist.
>>> 
>>> Can they be true or false? That is to say, do they have meanings?
>> 
>> 
>> The following situation could happen:
>> 
>> (1) Theory 1 could be compatible with explanation 1 of problem 1 and theory 2 could be compatible with explanation 2 of problem 2. 
>> (2) Theories 1 and 2 both have implications for problem 3 that makes comparison between theories 1 and 2 possible. 
>> (3) If theory 1 was refuted and theory 2 was not, then that would be a refutation of explanation 1 as well. 
>> (4) That refutation would be a result of refuting theory 1 with problem 3.
> 
> I don't know. I'm trying to think of examples of 1, 2, 3 and 4 with the above properties, with things like "1"= "General relativity", "2" = "quantum theory", and so on. No doubt they exist but I don't get what situation you're referring to. For a start, theories *are* explanations, so I don't know why your scheme has an extra level of indirection "Theory 1 ... compatible with explanation 1 ... of problem 1". Is that something like: general relativity is compatible with the geocentric explanation of the problem of why the planets have retrograde motions"?

Yes. The reason for the extra level of indirection is that if two theories don't apply to the same problem then there has to be some indirect link between them if any problem is going to be relevant to both of them.

>> Do you have this in mind or something else?
> 
> I think so. I have in mind something like: our best explanation (namely general relativity) of why objects with different attributes fall at the same acceleration under gravity is better than our best explanation (namely sheer chance) about why the sun and the moon seem to be very nearly the same size in the sky.
> 
> As always, "better explanations" mean "harder to vary".
> 
> "Harder" has to do with what other explanations would be spoiled by denying the explanation in question. So if you had a theory of planetary formation that required Newtonian mechanics rather than relativity, you'd have a lot more explaining to do before your theory could become a good explanation. But if you had a theory of planetary formation (consistent with relativity) that predicted that every solar system had bodies with those geometrical properties, thus contradicting the existing 'chance' explanation, that would be fine.
> 
> I chose these examples because they also illustrate that calling an explanation 'better', qua explanation, is not the same as calling it more likely to be true. (The latter would be an example of justificationism.) It isn't even the same as 'expecting it not to be overturned any time soon' (which isn't justificationism). In this case, I happen to expect that the exceedingly good explanation general relativity *will* be overturned, but that the moderately good 'chance' theory of the Earth-moon-sun geometry will not be.


What problem does this solve?

Alan