Steve Hays forwarded an article on to me that dealt in some aspects with a many-worlds scenario. Since I am not going to rebut that article specifically in this post, it’s not necessary to link to it. Suffice to say that it got me thinking about the nature of epistemology in a many-worlds scenario.

There are many ways to get to a many-worlds scenario. The most common currently is the idea of the multiverse, where the universe splits at every quantum decision. This was proposed as way of reconciling the seemingly contradictory data we get when conducting experiments such as the double-slit experiment. Or we can propose an infinite expansion of the universe where there will be pockets of individual universes within the multiverse (which is all the universes combined). These pockets are formed because space expands at a geometrical rate, and as such after a certain distance space expands faster than the speed of light, so an observer will never be able to observe what goes on after a certain distance. Each of these pockets form their own universes of observation, and in an infinite expansion there will be an infinite number of these.

Now there are many potential things we could talk about if we assume this theory is true—and indeed, if the theory is true, in an infinite number of alternate universes I did discuss those other aspects of the theory. Further, in some of those universes I actually will come to the exact opposite conclusions that I come to in this universe. After all, even if we have an infinite number of universes, we only have a finite amount of matter in each universe (which is the case because the expansion of the multiverse limits the amount of matter that can be observed in each universe, and since nothing travels through space faster than the speed of light, matter that is beyond the range of observation wouldn’t affect the individual universes). If we have a finite amount of matter in an infinite number of universes, the same universe will repeat itself, as will all other possible universes. Thus, in an infinite number of universes I am writing this post; in an infinite number of other universes, I am writing the exact opposite of this post. Finally, in an infinite number of other universes than the previous two, I did not even exist to write anything in the first place, etc.

This brings up an interesting question as to epistemology. Let’s just examine one particular aspect (again, assuming this theory is true): supernatural claims. There are an infinite number of worlds that exist wherein a burning bush appeared to Moses. (Note: even if Moses is a mythical figure in our universe, he must exist in an infinite number of other universes with the exact same result as recorded in Exodus.) Further, there are an infinite number of universes where someone named Jesus was crucified and rose again on the third day. (There are other universes where Jesus was crucified and rose on the second day, or the fourth day, etc. too).

Now here’s the thing: if there are an infinite number of universes where this occurred, how can we say that these events did not occur in this particular universe? In reality, since there would be universes where this did occur, and since there would also be universes where this did not occur yet where it is claimed that it did occur, then the epistemological question rears its head: how do we know which type of universe we are in?

This is brought to bear even more clearly when we consider quantum splits too. If there are an infinite number of universes, then there exist universes in which the quantum selection always yields the result expected by classical Newtonian physics. In other words, there must exist an infinite number of universes wherein photons going through a double-slit experiment will always land as they would if classical physics were correct. In such a world, no one would ever discover quantum mechanics. In fact, since quantum mechanics acts in that world identically to the world we get in Newtonian physics, then there would be no reason to say that QM is actually at work in that universe—even though QM is the reason that universe exists.

We can carry that further. There exist an infinite number of worlds that, up until this point in time, act exactly like ours, but which tomorrow will have such results as every subatomic particle in the Sun quantum-leaping to Pluto’s orbit. Now the question is: how do we know that our universe is not one of those universes where this will occur? We cannot use the “It’s very improbable that this will occur” excuse, because we have an infinite number of worlds to deal with—it will happen in an infinite number of worlds even as it does not happen in a different infinite number of worlds. It is impossible to use “odds” to determine whether or not it will happen in this particular universe without knowing which particular universe out of the infinite universes we are in.

The upshot of all this is that if the many-worlds idea is true, it is impossible to know anything at all. Ultimately, what you know is actually the result of a quantum split that did not occur in an infinite number of other universes. For the atheists, there are an infinite number of worlds where you are theists, and the reason you are an atheist in this world has nothing to do with reason—it has to do with the fact that in this world, the quantum split didn’t occur like it did in other worlds. The same is true of theists. The same is true for any belief, including the beliefs expressed in this post.

In short, if we use the many-worlds scenario to explain why something happens, we are cutting ourselves off from the ability to explain anything at all. Many-world scenarios cannot coexist with a scientific epistemology.