Introduction

Like the Sirens singing to Ulysses, the concept of entropy has tempted many a thinker to abandon the straight and narrow course. The concept is well-defined for chambers of gases. However, the temptation to extend the concept has been all but irresistible. As a result, entropy is used as a metaphor for uncertainty and disorder. We have nothing against such extensions of usage and, in fact, will indulge in it ourselves. However, we do believe that the price of metaphor is eternal vigilance.

One example of the temptation can be found in R. A. Fisher's Genetical Theory of Natural Selection? In the second chapter of that book, Fisher states a result that he dubs the fundamental theorem of natural selection. The theorem states that the average fitness of the organisms in a population increases under selection, and does so at a rate given by the additive genetic variance in fitness. Fisher then proposes the following analogy:

Fisher then quotes Eddington's famous remark that ‘the law that entropy always increases – the second law of thermodynamics – holds, I think, the supreme position among the laws of nature.’