As I have stated, I don´t think any one individual should have epistemic warrant to hold both, because, of how rational intuition works and how coherence work, specially, with respect to states of affairs that are either necessary or impossible.
If one is having a rational intuitions of a proposition p, that states that some concept A, wich is necessary or impossible, is coherent, in a given high cognitive state Level L, in a possetion of a richly enough concept repertoire C, such that if one were to seek a theory systematization of those intuitions, those systematizations would support p, and, such that for any other L' and C' , such that L' is greater than L and C' is contains C, and the given theory systematization would support p, then,
It is very plausibly the case that it is impossible that one would have intuitions of ~p for any L'' and C'' , where L'' is equal or greater than L, and C'' contains C.
Please excuse my imprecise statements, I can see after you have pointed it out.
It seems to me that the beef you and cnearing have with each other is over whether or not coherency supports possibility (is this correct?). I would think that while coherency is a necessary condition for possibility, it isn't a sufficient condition for possibility. It is for this reason that I don't think coherency alone of either MGB or ~MGB is sufficient to grant it's possibility.
Correct me if this is wrong but my idea of coherency is that something is logically consistent; that [merely] as a concept, it is meaningful. I.e. "a red colourless car" is meaningless. Coherency means that what we are saying isn't just literal gibberish.
In contrast, my idea of possibility is that something could actually be instantiated in some possible world.
So while coherency deals with meaning and logic, possibility has something to say about the limitations of reality - what reality can or could have included, i.e. possible worlds.
To me, there is an enormous chasm between these two, the latter being much more difficult to prove. I'm not entirely sure how we could even know if certain concepts are possible, or to even know what is and what isn't a possible world. It seems hugely speculative to say that because a concept has meaning in my mind and is logically consistent, it could be possible to exist in the actual world (or it exists in some possible world). Do you think that in principle, something can be coherent and yet impossible? I.e. does coherency necessitate possibility? if so, why? If not, then why should coherency alone be a sufficient reason to accept possibility?
Hi Jockito.
Even if some A is not a sufficient condition for a B, but only a necessary condition for B, A would usually qualify as evidence for B, under several accounts of evidence.
I don´t want to derail our conversation on other topics (like probability) , but, to try one approach, to illustrate: a probabilistic account of evidence would have it that x is evidence for y if P(y|x) > P(y) (probability of y given x, is higher than the antecedent probability of y) , and by bayes theorem:
P( B|A) = P( A| B) * P(B)/P( A)
then if we check when the evidence critiera (P(y|x) > P(y) ) applies
P( B|A) = P( A| B) * P(B)/P( A) > P(B)
which yields
P(A|B) > P(A) , Since A is a necessary condition for B, B predicts 100% that A, then, P(A|B) = 1, thus, as long as the antecedent probability of A is not 1, A is evidence for B.
So, as I agree and you state "coherency is a necessary condition for possibility" implies that coherence is evidence for possibility.
With that out of the way, coherency is that something is logically consistent, mostly, when it comes to coherent propositions, when it comes to a concept, at least, in philosophical research it is a much more richer and complex concept, in fact, it is a debated question, and, there are several accounts of what it is, and how/why/when it obtains.
In very general terms, a cathegory of coherent concepts is a class of concepts that "hang" together, there are several measures of coherence, depending on the account.
One account that might be illuminating is that concepts are the knowledge of our theories of the world , or at least are embeded in our knowledge of the world, here, theory and knowledge does not refere specifically to achademic knowledge, but, very broadly to any explanations we construct of the world, even those that are subconsciously built in the background (in the back of our heads, to put it some way).
Two relevant concepts are the internal structure of the conceptual cathegory that deals with ways features relate (e.g structure function relations, causal schemata, etc...), and the other, is the role the concept plays on the backgrond of our knowledge, how it fits in "the cosmic machine" (Quine) that is our minds.
My example about evidence above, should close somewhat that chasm, but, if it does not, you need to avoid running, inadvertenly, an argument from incredulity (which is fallacious reasoning), the chasm could plausibly be fixed by reading on the subject.
Nevertheless, I don´t see what is the problem in approaching the question of if something is possible or not, we do this all the time, with various degrees of success, depending on the matter (its complexity,etc...).
I don´t think anyone doubts that it is possible that aliens exist, now, there are two ways of saying this, one is that it is as far as we know (we have not determine that it is false) aliens exist , this is what is called epistemic possibility, but, there is also another type of possibility we are taping in, and that is metaphysical or broadly logical possibility, when we think or say that it is possible that aliens exist (in the epistemic possibility sense) we also mean in the broadly logical possibility sense, because, if we thought that aliens were like 2+2=5 or, spheric cubes, we would right, then and there, deny that it is possible (in any sense) that they exist , even merely, in the epistemic sense, but in fact, the contrary is the case, even if it turned out that aliens do not in fact exist, most would still think that it is possible (in the broadly logical possibility sense) that they do, that they could exist, nevertheless.
There is nothing much speculative, in that our cognitive faculties allows to aproximate reality (what is, what is not, what could be, what couldn´t be, what has to be), defeasibly, imperfectly, but persistently.
As far as I can tell, absolute incoherency wich implies logical inconsistency, implies impossibility(as you said it is a necessary condition for possibility).
I hope it helps.
I should be in bed by now, good night.
