Imagine the following scenario. You are put before a firing squad as punishment for a serious crime. Ten expert marksmen are lined up, each with his rifle cocked and loaded, and pointing at your head. You grit your teeth, close your eyes, and prepare as best you can to face your seemingly inevitable demise. The roar of the ten rifles explodes in your ears...
... but you’re still alive. Gingerly, you open your eyes to discover, to your amazement, that all ten expert marksmen have missed the target completely. Similarly astonished, the leader of the squad decides, in a fit of sympathy, to let you walk free.
Given time to reflect on what has happened, two options present themselves. The first would be to, quite rightly I think, demand an explanation for why the extremely unlikely scenario you just endured happened in the first place. The second would be to shrug your shoulders, think nothing more of it, and then return to your life, putting the event down to mere coincidence.
Having decided, as any rational person would, to rule out blind chance and seek to explain the scenario, we are presented with only two possibilities. One is that a million different firings all took place on the same day as yours. If the chances of ten expert marksmen all independently missing the target are one in a million, then given a million firings, we would expect one to fail. It seems that yours was the one which failed; and though you are lucky, this isn’t so surprising, since we would expect one firing to fail anyway.
The second explanation, given that yours was the only firing taking place that day, is that something suspicious is going on. Either the marksmen were all told to miss, or they were equipped with blank ammunition, or something similar. There was intention/design behind the occurrence which explains why it happened.
The firing squad story presents a direct analogy with the existence of the universe. We know from science that the physical constants needed to produce a developed universe at all are ‘fine-tuned’ - that they had to fall within an infinitesimally small range of values (http://en.wikipedia.org/wiki/Fine-tuned_universe). The very existence of a stable, developed universe such as ours is inherently unlikely. Given this widely accepted view, and since it is not rational, given the odds, to put things down to chance here (as the firing squad analogy clearly suggests), we have two main options. A million universes? Or intention/design. The first of these is the ‘multiverse’, the hypothesis that our universe is one of many universes existing in parallel. The second option is...well...suggestive of something else; something quite different.