This is a fascinating discussion list, full of stimulating ideas and theories, but I would be interested to know what people *actually* believe on the subject of many/all worlds - what one would bet one's house or life on, given that one were forced to choose some such bet.
For my own part, I give strong credibility (>50%) to the existence of many worlds in some guise or other, and in particular to the existence of all logically possible(*) worlds (alpw). For me the existence of one world (ours) so conveniently life-suited - sufficiently spatio-temporally extended and quiescent but with particular properties enabling wide diversity in chemistry etc - demands a specific explanation, and the only other candidate final explanation - a Creator (say a God, or a 'higher' civilisation) - suffers (at least) the problem of requiring an explanation for *it*. (For the supposedly main problem of alpw - why we are not in one of the apparently far greater number of worlds where physical laws are clearly violated from now on, if alpw were to exist - solutions have already been posted - see for example http://www.escribe.com/science/theory/m1909.html or http://www.escribe.com/science/theory/m3348.html .) More fundamentally, if we even consider the question 'how is it that we exist?' to be a reasonable *question*, then we have to concede the possibility that things could have been different (different physics, or nothingness, for examples). Any constraining mechanism (eg the laws of physics) on the full range of logical possibilities must itself have an explanation: the scope of all logical possibilities can never seem to be tamed at the end of the day, and always appears to emerge as an almost inevitable final explanation. One must always consider that there could be explanations for our existence totally beyond our comprehension, but given that we already have a satisfactory explanation (existence of alpw), we have no need to give these a high credibility. (*) logically possible: that which does not entail any violation of deductive logic. Alastair