In one school of thought it is customary to begin discussions of galactic life by appeal to Drake's equation and then to proceed to a detailed examination of the numerical magnitude of one or more of the string of factors whose values have to be estimated. An example of this procedure is furnished by Michael H. Hart's analysis (Chapter 22), in which he concentrates on the probability that 600 or more nucleotides might line up in the right order; then he proposes that one of the factors may be very much less than 10–30. Of course, 10–30 is already very small, and, if included as a factor in almost any expression having to do with the physical universe, will cut the product down to negligible size. In this application the conclusion is that the number of technological civilizations independently arising in a galaxy is very much less than 1. Well, this may be an excess of zeal, and many of those addicted to the use of Drake's equation would, in similar circumstances, have arranged for the product to emerge with an order of magnitude around unity because, after all, a calculation condemns itself if it seriously contradicts the possibility of the one technological civilization we know about, namely our own.

But is Drake's equation correct? It seems that it suffers from oversimplification - surely at least one plus sign ought to be there.