The Language of Worlds

The idea that there might be worlds besides our own shows up in at least three fields. In physics the idea is used as an interpretation of quantum mechanics or as an explanation for the existence of a life-conducive world. In the philosophy of logic, the same language is used to talk about possible worlds which may or may not be thought of as actually existing. In fiction, the idea refers to the possibility of different cosmoi possessing subtly different laws of nature or existing organisms and where at least one cosmos is accessible from at least one another.

In only one of these cases, the fiction case, could we encounter the contents of the other worlds in the same way that we encounter the contents of this world. In both the physics case and the philosophy case, the worlds are supposed to be self-contained. If we can access them at all, it is not in the same way that we access our own world.

It has been argued by Saul Kripke in Naming and Necessity that since Sherlock Holmes was made up by Arthur Conan Doyle, he is necessarily made up by Arthur Conan Doyle. This is a direct consequence of the necessity of origins. Thus, there would be no logically possible world where what we call Sherlock Holmes exists except as such a fiction. The same would be true of other fictions, such as unicorns.

This has some odd consequences. For one, if we found that we lived in the fictional kind of multiple worlds scenario, where different worlds are interaccessible, then we might find ourselves visiting a world where, we would usually say, "unicorns exist." Suppose in our fictional scenario that we had just invented a very difficult device allowing us to transfer between worlds and had good evidence that such a device had never existed in our world. If we agree with Kripke's argument, then, since we were thinking that our myth of the unicorn could not have came from this world, we would be wrong. In our world, unicorns are mythical, whereas in this other world they are not.

Supposing we found that one of these other worlds came into being differently from our own, so that everything in it originated differently from everything in our world. In that case, we would have to say that anything we met in other worlds would be different from anything we encountered in our own world in virtue of originating in a different manner. Thus, if we found a world where the Norse deities were real and the Norse creation story was real, then we would have to claim that what we called dirt in our world and what they called dirt in the Norse world would be different in virtue of having different origins. In fact, it is at least likely that the same would go for matter and energy as well. None of this requires the laws of physics to be radically different. I am not pointing out that water might be XYZ instead of H2O in the Norse world, but that hydrogen atoms, as a class, might have originated differently in the Norse world. The humans of the Norse world would likely have originated differently from the humans of our world, and thus would not both be what we call "humans."

In the physics case, this problem is largely avoided. Subatomic particles will generally originate in the same manner in each world. The various worlds only vary within certain bounds. Each world would, itself, originate in a similar manner. Likewise, in the philosophical case, the logical worlds, by definition, only represent possible states of affairs. Some included horses with a single horn, but also the proposition that these are not unicorns in our sense of the term. Even if logically possible worlds exist independently of thinkers, which I doubt, this does not case the kind of trouble which interaccessible worlds would cause.

Now, one may be wondering whether I am interpreting the necessity of origins too stringently. I have applied it to kinds, and one might think that, while it is necessary for a thing to be the kind of thing it is, and it is necessary for a thing to have the origins it has, it is not necessary for a kind to have the origins it has. In that case, while any Sherlock Holmes look- and act-a-like we might meet would still not be our Sherlock Holmes, the unicorns might still be unicorns in our sense of the term, and H2O in the Norse world might still be what we call water in our world. This is a dispute about how names work. I do not think that Kripke's argument allows for this nuance, although I do not have it in front of me at the moment.