Ockham's Razors

Most readers will be familiar with Occam's razor or the principle of parsimony that states that simpler theories are better than more complex ones, other things being equal. This must be the most comprehensive treatment of the subject, providing as it does a history, parsimony in evolutionary biology, then in psychology with respect to chimpanzee mind-reading, and in philosophy. The history chapter explains a variety of versions, starting with Aristotle's principle that nature does nothing in vain and the covering argument between geocentric and heliocentric astronomy. In the case of Newton, his formulation is that 'no more causes of natural things should be admitted than are both true and sufficient to explain their phenomena.' This naturalistic thought is taken up by Hume on the uniformity of nature, an argument he uses to dismiss the evidence for miracles. John Stuart Mill offers a more subtle formulation that we should not believe anything for which there is no evidence: the principle is methodological rather than ontological - to do with ways of knowing rather than the nature of reality.

There is an extensive discussion of Bayes and Bayesianism concerning the probability assigned to a hypothesis in the light of new evidence. Sober compares this with the idea of model selection and the falsification approach of Popper. In the psychology chapter, the author asks if chimpanzees are mind readers or just behaviour readers, which brings up the problem of blackbox influence - in this case the mechanisms or intervening variables that mediate the connection between stimulus and response. The last chapter may be of most interest to readers as it discusses atheism and the problem of evil as well as the mind-body problem and the causal efficacy of the mental. These raise the question of naturalism and identity theory where answers will depend on prior commitments and one's overall worldview. For me the important point is to use the principle with integrity rather than as a knee-jerk reaction in defence of naturalism and materialism. This book gives a subtle insight into the scope and limits of Occam's razor.