• Metaphysician Undercover
    3.8k
    This is precisely the issue in reverse though - what are the criteria for impossibility? Are we talking about physical impossibility, logical impossibility.... Each will have different criteria presumably, just like "possibility" under my contention.MetaphysicsNow

    I don't think this is the case, so long as we stick to customary definitions when determining logical impossibilities. We describe physical things with words, and our definitions are based on those descriptions. So logical impossibility, which is based in contradiction is a derivative of physical impossibility. It is one coherent set of criteria.

    When we approach from the other way, "possibility", we have all sorts of random criteria as to what constitutes possibility, allowing for infinite possibility. This is why we must approach from "impossible" rather than "possible". Do you see that one of them "impossible" is a principle of constraint, while "possible" is inherently unconstrained? The unconstrained is unintelligible, while constraints are intelligible. So we proceed in obtaining certainty in knowledge by determining what is impossible, because "possible" can't give certainty but "impossible" does.
  • MetaphysicsNow
    151
    Do you see that one of them "impossible" is a principle of constraint,
    No, I don't see this, since as I pointed out, what is going to count as impossible is going to change depending on the circumstances just as much as what is possible.

    When we approach from the other way, "possibility", we have all sorts of random criteria as to what constitutes possibility, allowing for infinite possibility

    Firstly, the criteria I mentioned for possibility are not random in the least. One set of criteria constrains the possible within the bounds of the known laws of nature. Another set releases that restriction but applies the laws of classical logic. Those are not random criteria, but clear and precise ones.

    Secondly, nothing you say about the impossible rules out their being infinite impossibilities.

    "Possible" and "impossible" are terms that come together as a package or not at all.
  • Metaphysician Undercover
    3.8k
    No, I don't see this, since as I pointed out, what is going to count as impossible is going to change depending on the circumstances just as much as what is possible.MetaphysicsNow

    Right, so knowing what is impossible requires knowing the circumstances. The circumstances dictate what is impossible, and knowing what is impossible allows one to say what is possible. Do you see how impossibility, according to circumstances, makes possibilities true and intelligible rather than infinite and unintelligible?

    The criteria for what is possible does not change depending on the circumstances. Nor does the criteria for what is impossible change depending on the circumstances. But particular things which are impossible are determined according to the circumstances, and by determining these impossibilities we can limit what is possible, to less than infinite. Without such limiting, possibility is just meaningless nonsense, unintelligible. So this is the point, we bring possibility into the realm of intelligibility by limiting it with "impossible".

    Firstly, the criteria I mentioned for possibility are not random in the least. One set of criteria constrains the possible within the bounds of the known laws of nature. Another set releases that restriction but applies the laws of classical logic. Those are not random criteria, but clear and precise ones.MetaphysicsNow

    Your first set of criteria restricts possibility according to "known" laws. This is ambiguous, and not a true restriction. What is "known" varies from one individual to another, such that what is possible for me is different from what is possible for you, under the same circumstances. And, what is truly possible under those circumstances is completely different from either of these, due to the failings of human knowledge in general.

    Your second set is just a more ambiguous form of the first, allowing that an individual when determining possibilities may have disregard for the laws of nature, as known by that individual, and only have respect for the fundamental laws of logic. These possibilities are likely less true than the first.

    Those two sets of criteria offer no approach to true possibility.

    Secondly, nothing you say about the impossible rules out their being infinite impossibilities.MetaphysicsNow

    I don't know what you mean by "infinite impossibilities". That is itself an unintelligible phrase. That something is impossible is a determination made by a mind, a judgement. A mind cannot make an infinite number of judgements. That is the first impossibility which we can determine. It is impossible that there are infinite impossibilities.

    Possible" and "impossible" are terms that come together as a package or not at all.MetaphysicsNow

    This is not necessarily the case. Logicians who speak of infinite possibilities necessarily imply possibility without impossibility. That is the gist of the point I am making. Possible and impossible do not necessarily come together as a package. We can premise possible without impossible, and this gives the appearance of an acceptable premise. However, it is a false premise so we must deny it and insist that possible cannot come without impossible.
  • MetaphysicsNow
    151
    Nope, you've lost me completely - I'll have to move on to other posts.
  • MetaphysicsNow
    151
    But I cannot resist one last parting word before moving on - I know, it's a weakness of mine:
    Consider the following schemas:
    1) It is possible that P
    2) It is impossible that P
    3) It is not possible that P
    4) It is not impossible that P

    Here P stands in for some proposition or other.
    Let's suppose for the moment that P is the proposition that "The round copula is square".
    Well, since anything that is round is not square, substituting this value for P into 1 and 4 gives you a falsehood, and into 2) and 3) gives you a truth. So, there is at least one impossibility. Here's another P = "An inedible apple is perfectly edible". So that's two impossibilities, and I've only just gotten started.
    Now let P="Some grass is red". Under this substitution 1) and 4) gives you truth, whilst 2) and 3) gives you falsehood. Another substitution with the same result: P="There are green swans". So, two possibilities, and I could keep going.
    What is the point of all this? Two things:
    1) Whatever you think of possibility or impossibility there are indefinitely many specific possibilities and impossibilities.
    2) The schemas 1 and 4 are logically equivalent, as are 2 and 3. This means we can define the possible in terms of the impossible and vice versa - the logical equivalence implies that they are two sides of one and the same coin, that coin being the concept of modality.
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