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An attempt to reason about why our world is the way it is.  A Christian believes Many people believe  that the world is created. However, this belief is not shared by everyone, so it's worth thinking about what this means. If the world is created, then it's likely to be the way it is because its Creator\footnote{Not everybody that believes that the world is created thinks that God created it. Still, I hope that they would agree that naming the creator of this world as "the Creator" is reasonable.} wanted it to have certain properties so in order to understand why our world works the way it does, one would need to understand the intent of its Creator. While it that  is worth thinking about it, interesting in itself,  I will not try to pursue this path here. Let us consider the other case. If the world was not created, then there may be other worlds\footnote{We don't have any proof for the existence of other worlds, but one could expect them to exist for the same reason that ours exists. If ours has no reason at all for existing, which is likely if it is not created, then it's likely that other worlds would also not need any reason for existing and would simply be. However, for this paper it does not matter if there are other worlds or not.}. Even if there aren't other worlds, ours could have been different. We will denote by \definitie{possible worlds} these other worlds that either are or could have been. \section{Possible \section{Modelling possible  worlds} First, let us note that two different possible worlds should not interact between them. If they are interacting, it's more reasonable to say that they are actually a single possible world with two parts.  How would a possible world look like? It could have exactly the same fundamental laws as ours, but with the matter organized differently. It could have similar laws, but with different universal constants. It could have different fundamental particles (or whatever the basic building blocks of our universe are, assuming that there are any). Or it could be completely different, i.e. different in all possible ways.  It could be that our logic and reasoning are universal instruments, but it could also be that some of these possible worlds could be beyond what our reasoning can grasp and others could have properties for which our logic is flawed. Aknowledging that, let us see if we can say anything about the possible worlds that we could understand and could model in some way. In the following, the \definitie{possible worlds} term will denote only the possible worlds which we could model (including models which need an infinitely long description, but which still follow our rules for reasoning).  This notion of "model" is not precise enough. Let us restrict the "possible worlds" term even more, to the possible worlds that we could model mathematically, even if that may leave out some worlds. We will also do the reverse and say that any non-contradictory non-contradictory, at most countable\footnote{We could also go beyond countable axiom sets, but that would complicate things without any benefit.}  set of axioms models some possible worlds\footnote{Even if some of those models seem outlandish, there could be something that follows those rules and that is completely separated from anything else, not interacting with any other universe in any way. I would say that this something would be an universe. If you don't like it, in the following I am going to restrict what I call a possible universe.}. If there isn't any designer for our world then we have no way of preferring a world over another, except that there is one of them in which we live. In other words, if our world is the only one that exists, then any other possible world is as likely to have existed as well. If multiple worlds exist, by picking a random world, ours has a the same chance of being picked as any other.  If there isn't any designer for our world then we have no way of preferring one over the other, except that there is one of them in which we live. It seems that reasoning about all the possible worlds could be very hard, but maybe we could do something easier, maybe we could reason about the mathematical axioms that model the worlds. Let us consider the set of axioms that define a monoid. All groups are models for this set of axioms, but intuitively a group is something more interesting than a monoid and we should include extra axioms for defining it. On the other hand, we could include all possible axioms for each model (e.g. for each monoid), uniquely identifying it, but again, intuitively this is not a useful way of modeling. We will call these the "too-specific problem" "too-general" problem  and the "too-general" "too-specific"  problem. For a given world, a much better good  set of axioms would be one that would allow us to make all possible predictions for that world. The term prediction is not a clear one. To make it more clear, let us restrict again the "possible worlds" term. One option would be to make it to denote all possible worlds that/which? have a concept of time (which is something reasonably well ordered), that/which have and  a concept of the state of the world at a given time and for which describing the state of the world at all possible times is equivalent to describing the world. This ignores some important issues like the fact that it's reasonable to have a concept of time without having a well defined concept of "the state of the world at a given time", so we should could  rephrase the definition above to include many other  reasonable notions of space and time, e.g. for we can include  worlds where "point" is a concept and we can know which pairs (point, time) are before a given (point, time) pair. Then when  we can say that prediction would mean predicting we can \definitie{predict} something means that we have a system of axioms for which  the state of the world (maybe at a given point) from is uniquely determined by  the state of the world at a subset of the previous points in time. time\footnote{Will be extended to statistical predictions in the next paragraph}.  If we are interested in predicting the state at a given point $P$, this subset should include a full section through $P$'s past (e.g. a plane which intersects it's past cone), i.e. it should separate $P$'s past in two parts, one which is "before the subset" and one which is "after the subset"; subset"\footnote{This means that  all lines which fully lie in $P$'s past and connect a point which is before the subset with a point which is after the subset must go through the subset. subset}.  One could think of similar definitions for predicting the entire state of the world. If needed, this definition could be changed to work for more concepts of space and time. In a deterministic universe, knowing the laws of the universe and its full state we could, in theory, fully predict $P$'s state. But an universe does not have to be deterministic and, even if it is, one could have only a statistical model for it. Then a set of axioms which only allows statistical predictions (I'll call this a \definitie{statistical axiom set}) is fine and for the purpose of this document we don't need to make a difference between a non-deterministic universe and a deterministic one but for which we only have a statistical model.   If we define "prediction" in some useful way, as suggested above, and restrict the "possible worlds" term to the ones where we can make predictions, then it makes sense to use only systems of axioms that allow predictions. We will always use the best possible system for predictions (statistical or not). This solves the "too-general problem" since such a system would describe its possible worlds in a way that does not leave out important things. Still, there is nothing that prevents such a system from going into too much details.