I think you are misunderstanding me. What is technically possible is a proper subset of what is physically possible, and what is physically possible is a proper subset of what is logically possible. But what is epistemically possible is not a proper subset of any of these, as what is epistemically possible is dependent upon a particular individual's state of knowledge. It may be that a complex contradiction, for example, may not be recognized as a contradiction by someone, and so it may be epistemically possible for someone.

Basically, the less one knows, the more things are epistemically possible. This explains why people who know little or nothing about how science works often imagine all sorts of silly things are "possible".

So, if "realizable possibility" meant "epistemic possibility", then it would not be a proper subset of what is physically possible.

You mean that only what is actual is a real possibility? Hmm. So nothing can be a real possibility unless it is actual. Maybe, but it sort of undermines the point of saying that something is possible. Don't you think? I used to think that some real possibilities were maybe not actual, but that they really could be real for all we knew. For instance, that there are ET's are real possibilities since for all we know, there are ETs. But I guess I won't think that anymore.

No, i believe every possible ways things could be, exist. If we accept this assumption, .

But why should anyone accept that? It is obviously false. It is possible that McCain (or anyone) is president rather than Obama. Alas! Alas!.

I think, though, we had better simply let U. say what is meant by the cryptic phrase, "realizable possibility", as on the face of it, it is redundant, but is close to saying something that isn't (such as your "real possibility" or my "realistic possibility").

But why should anyone accept that? It is obviously false. It is possible that McCain (or anyone) is president rather than Obama. Alas! Alas!.

It may help to contrast realisable possibilities or real possibilities with pure possibilities.

---------- Post added 05-12-2010 at 03:43 AM ----------



The time has passed. That is no longer a realisable possibility.

But it was, I fervently hope!

Did i kill your hopes? I take it that you don ` t want to debate this point with me? Don` t give up so soon.

For most people who are chess amateurs, although checkmating an opponent with only two bishops and a king is a possibility, it is not a realizable possibility. They don't know how to do it, at least within the 50 move limit. "Realizable" in the phrase, "realizable possibility" gets its meaning from what is not possible within certain parameters, and not from what is possible within those parameters.

I have no interest in that topic. Good bye.

But it isn't a possibility at all. So you could just say "Me taking flight by flapping my arms is not a possibility".

No, i believe every possible ways things could be, exist. If we accept this assumption, then ordinary talk of probability like "It is highly probable that he came home" can translated to "In most possible worlds similar in kind to our world, he came home". etc..

Then why have you been participating in the discussion? Most odd!

No. I was trying to advocate modal realism. You are interested in something different.It isI funny that you think everything is odd if you don` t know it. You must be saying odd all the time.

Touche'!............

I'm somewhat familiar with this way of talking about possible worlds. It reminds one almost immediately of multiple universes posited by some theorists in physics. Are logically possible worlds and multiverse related in some important way. I think the two may have grown up together in the same nursery perhaps.

Looking around a bit I find (and correct me if I'm wrong) that the terminology "possible worlds" is attributed to Kripke in the late 1950's at Harvard. Similarly the terminology "quantum multiverse" is attributed to Everette around the same time at Princeton.

I'm guessing the history of the two ideas is deeply related (though the logical manifestation of theme is much older). Oddly, I notice that the wiki article for Multiverse makes no mention of Kripke and the article for "Possible words" makes no mention of Everette.

Possible world - Wikipedia, the free encyclopedia

Multiverse - Wikipedia, the free encyclopedia

However, Google searches for "Kripke" and "Everett" do yield quite a few hits.

I do think that since what causes* the many universes is something different from what causes* the many possible worlds but in what ways might it be the same.

We have a whole set of words to deal with: possible, probable, actual, realisable etc. Logic, mathematics and physics (especially quantum physics) in some areas become indistinguishable. Is this one of those areas?



* I'm going with the broader Aristotelean concept of causality here.

Today, this was posted:Personally, I dont see any difficulty in understanding what is meant by a realisable possibility. Nevertheless, I'm informed that neither I nor anyone else knows what this phrase means. I would be interested to know whether readers find this phrase obscure, unclear, readily comprehensible, or whatever.

As to the multiverse proposted by Everett, it is extremely conservative in my opinion. According to Everett, the wave function central to Quantum mechanics never "collapses", but branch out at each quantum event. There is a quantum event that lead you to talk to the girl in the counter, and there is an event where you don` t. Both events bifurcate to different worlds where you do, and you don` t. This endless spliting of worlds at every quantum event are conservative in my opinion, because in all the worlds, they all are still obeying the rules of quantum mechanics. I think there are worlds obeying different equations all together.