Let me begin by differentiating reality from possibility. What I mean by other possible worlds is our conscious power to imagine and deduce outcomes, possibilities and consequences. For example, I am sitting here in front of a computer typing, but I could be out having a beer with my friends. Thus, there is another possible world that is just the same as this one, except that I am not sitting in front of the computer in this other world, but instead I am drinking beer with my friends. This other world is relatively closer to reality than is the world in which I was not born at all, or in which I am someone completely different and doing different activities from what I am doing in reality. Possible worlds exists only in the imagination for some period of time. The possible worlds that I have the power to turn into reality as a result of my own decisions are closer to reality.
The possible worlds in this view do not cross paths (ie., they are parallel) and it is impossible to cross over to other worlds. However, I can imagine a world in which I am having a cup of tea, and another world in which I am not, and then turn the imaginary world of me having tea into reality, simply by deciding to make myself some tea. We need to combine the concept of possible worlds (fig1) with the following picture of free will and decision making:
At the crossroad, we exercise our freedom of will, and decide to pursue one course of action. With that decision, one possible world became reality. What lead up to the decision is a deliberation process that was sharply restricted by time constraints. Deliberation can be completely paralyzing if it does not lead to a decision in proper time, because at some point the deliberation becomes one of the options, and it is too late to see the movie or go to the café, and we have decided to deliberate all night instead of doing anything else. Deliberation is always only an option. One could live a life without deliberating at all, at least consciously, and only act. Thus we can either act one way, or another or to deliberate. Opportunity is bald in the back and so we must grab onto it before it passes us. Figure 4 is what we get when we combine free will with the notion of possible worlds.
The question arises at this point as to the 'reversibility' of decisions. Can two different choices result in the exact same world?fig 4