Statistical theory tends to impose this limitation on us. As a consequence we really know little about using statistical theory and methods to evaluate the probability of unique events. Two important concepts are directly involved with the application of probability to the origin of life. Even in a series of statistically acceptable random numbers, a non-random pattern may be detected. The point he makes is that it is not always easy to distinguish between random and non-random even under ideal conditions.
Impossibility is another relative term.
On the human scale events rarer than one in a million are essentially ignored. On the supercosmic scale he uses a number on the order of one in 10 n , where n is a number of more than 10 figures. Consider the following situation. This statement makes no sense from a biological or sociological point of view, but considered exclusively from statistical considerations it certainly does not contradict any experience. Suppose we consider a protein of molecular weight 100,000 which is composed of 830 amino acids in a particular order.