A common argument
often used against the spontaneous formation
, goes something like this:
The probability of life forming from non-life is about the same as the probability of a tornado going through a junkyar, and spontaneously assembling a full, working 747.
This is a very compelling image that is created here - imagine the news stories that would be caused by the random destructiveness assembling such a thing. It's something that sounds so unlikely that it seems certain it could never happen.
The problem here is that there's no reason to believe the analogy is of any value for comparison. Understanding the procedures involved in abiogenesis, though almost entirely theory right now, suggests there was no huge "jump" from just a soup of inorganic chemicals straight through to fully functional form of unicellular life complete with DNA and the like.