I'm new here. So, I might be unfamiliar with many things that have been talked about here. However, I noticed something about the Multiple Worlds theory-the fact that it contradicts itself. In the following paras, I'm going to express myself about this. If I'm not wrong, the theory claims the existence of multiple(infact, infinite realities) at the same time. We can only experience one of these realities at a time. This conclusion has been reached by taking the examples of subatomic particles like electrons that can make the transition from one energy state to another. Similarly, the theory says that it is possible for us to experience a reality totally different from what we experience all the time by making a transition from one reality to another. The number of possible realities is infinite, depending upon the point in history where events had taken a different turn from what actually happened in our very own reality. The lack of determinism in quantum theory, a consequence of the Heisenberg's uncertainty principle, is used to conclude that since an electron's position with respect to a certain velocity can't be exactly determined(or vice versa), it is possible for it to be in many places at one time, although it will be in only one place at a specific time. The number of possibilities is huge. Similarly, if this was true at the macroscopic level, we could possibly experience an infinite number of realities, only one of them at a particular time. However, Heisenberg's uncertainty principle has very little effect at the macroscopic level as the error in the determination of one physical quantity with respect to another is very little, almost negligible. So, the theory, in a certain way, says that what is true for the microscopic level must have little effect on the macroscopic level(since at the macroscopic level, one physical quantity can be determined with respect to another while this is not possible at the microscopic level). So, it follows from this that if separate realities are possible at the microscopic level, the same must not apply at the macroscopic level, i.e., it must have such a little effect at the macroscopic level that it can be neglected. This is something that is hard to understand because if any event changes at the macroscopic level, the whole course of history takes a different turn. Thus, there can be no negligible change at the macroscopic level. If anything at all changes, the change produced is always drastic. Thus, the theory contradicts itself. Some might say that the properties of macroscopic objects are based on those of the microscopic objects that make them up. However, the interactions between these microscopic objects changes the properties of these macroscopic objects. So, the behaviour experienced is not the same. I am not even going to talk about the strange behaviour of the indeterminate number ∞. It causes major problems for this hypothesis because it is not a useful number for modern physics, however useful a number it might be for mathematics. The concept of ∞ is always going to be a hypothetical one. I would conclude by saying that if there is any lack of determinism at all, it is in this theory itself. The theory hardly determines anything. I would rather consider it as science fiction rather than science fact.