Accessible Worlds

[aleph_0]

A new consideration: In that example, we agree to possibility of future action. How about possibility of the metaphysically given? For instance, could there have been eight planets rather than nine? I say, yes. It is possible that, rather than the universe having started with this distribution of matter, it could have been slightly different to cause there to be eight planets rather than nine. I know of no law of physics or logic which contradicts this point, since neither physics nor logic prescribe what must exist, but only how that which exists must behave. In essence, it is like feeding a different slab of meat into the same meat-grinder, and seeing what pops out.

[DavidOdden]

For instance, could there have been eight planets rather than nine? I say, yes. It is possible that, rather than the universe having started with this distribution of matter, it could have been slightly different to cause there to be eight planets rather than nine. I know of no law of physics or logic which contradicts this point, since neither physics nor logic prescribe what must exist, but only how that which exists must behave.

Something that has long bugged me about possible world semantics is that it punts on the concept "possible". So here's my proposal: we vote on your claim. I say that is not possible that there could be 8 planets rather than 9 (and let's stipulate something about the Vogons not having gotten here billions of years ago if we do this poll). I say "no". So democratically, we can decide if it is possible for there to have been 8 planets. (Insert comment about uncertainty as to whether there are 9 planets).

Under ordinary non-random physical-law assumptions, if you were to replay cosmic history, you'd get the same arrangement of planets from the same starting point. If you assume there are indeterminate causal relations, i.e. god throws dice (random dice, not determinate dice), then you don't even need to go back to a different initial distribution of stuff. So why then would you attribute anything special to initial distribution?

It seems to me that you're making special assumptions about "initial distribution", for example, you're denying the idea of universal uniformity. If you get to arbitrarily deny the principle of initial uniformity, then I get to assert that principle. So now you even understand why I say that 8 planets is not possible.

[aleph_0]

I'm not sure we have a large enough polling sample to determine whether this holds outside the realm of the forum, but if you want to just arbitrarily take the word 'possible' to indicate what is actual or could be actual by acts of will, we can. Then I'll just invent a new word, 'squadrable', which refers to all things that could be the case. I argue, in this category one is able to posit the existence of eight planets.

As for ordinary, non-random physical laws, I'm not convinced we can assume them nor that their contrary implies any kind of supernaturalism.

And I do not believe that talk of possibility denies initial uniformity but mere posits its lack--except that there is lack of uniformity in the following sense: In some places of the universe it is different from some other places (Chicago is not Hong-Kong, is not Andromeda). With this much, we can talk about how some part of the universe (say, ours) might have had some distribution other than it in fact did.

Although, to talk out-loud for a bit, the reason I have not been discussing counter-legals is because they seem to be nothing more than verbose talk of the concievable. For, in any situation where you're talking about a counter-legal you're talking about merely what you could imagine happening--say, in a dream. So why proliferate terms for the same concept? Likewise, though, this kind of possibility seems to be edging into the realm of the conceivable, with the exception that you maintain the known laws of physics. So it's not quite the set of [in principle] conceivable situations. So it still seems distinct enough from conceivability and distinct enough from man's potential to warrant its own category, the category of the possible (or, if you insist, the squadrable).

[y_feldblum]

How about possibility of the metaphysically given? For instance, could there have been eight planets rather than nine? I say, yes. It is possible that, rather than the universe having started with this distribution of matter, it could have been slightly different to cause there to be eight planets rather than nine. I know of no law of physics or logic which contradicts this point.

I say no.

By DavidOdden's theory of possibility, "no" would win, and it would therefore not be possible for there to have been eight planets.

But let me move to my theory of possibility. You take into account the referents of the laws of physics - the relationships between entities. But you fail to take into account the entities themselves (you say, "what if the entities were different?" - but they were not different). What was, was, and it was what it was. It was metaphysically impossible for the entities which existed before the solar system's to cause the creation of eight planets, because that potentiality did not exist. Epistemologically, from the perspective of now, we have full knowledge of the metaphysical possibilities of the entities before the solar system: they could and did become a solar system of nine planets, and they could not and did not become anything else. Epistemologically, supposing we had the perspective of a spacefarer before the solar system came to be, one has enough evidence that a solar system of some planets will form, but little knowledge of precisely how many planets. Then, from that perspective only, eight planets is an epistemological possibility, even if not an Aristotelian potentiality, a metaphysical possibility. (An epistemological possibility represents the degree of certainty one has regarding knowledge of a potentiality.) So no, it was never possible for there to be eight planets; and although I may not have had enough evidence to exclude the number eight back before the planets came to be, now I do have that evidence, and now I do exclude that number from the realm of possibility.

[aleph_0]

I say no.

By DavidOdden's theory of possibility, "no" would win, and it would therefore not be possible for there to have been eight planets.

Okay, but I'm interested in the squadrable.

But let me move to my theory of possibility. You take into account the referents of the laws of physics - the relationships between entities. But you fail to take into account the entities themselves (you say, "what if the entities were different?" - but they were not different). What was, was, and it was what it was.

Besides my "failure", nobody denies this.

It was metaphysically impossible for the entities which existed before the solar system's to cause the creation of eight planets, because that potentiality did not exist.

Why not?

Epistemologically, from the perspective of now, we have full knowledge of the metaphysical possibilities of the entities before the solar system: they could and did become a solar system of nine planets, and they could not and did not become anything else.

How do we know they could not have?

You have yet another notion of "possibility", epistemic possibility. It seems to me all together valid, since it conforms to how we sometimes speak (thus you are not arbitrarily proliferating new scientific terms), it is not internally contradictory, and makes a useful distinction. All the same, I don't see why metaphysical possibility--squadrability, or that of initial distribution--is invalid.