A form of methodological reductionism, it is the scientific mandate originating with William of Ockham (1285-1349), sometimes referred to as the ‘parsimony of postulates’, and summarised with the acronym KISS (‘keep it simple, stupid’). It contains the idea, fundamental to the scientific method, that one should not make more assumptions than the minimum needed or, equivalently, choose from a set of otherwise equivalent models or theories the simplest one. Isaac Newton (1642-1721) formulated it as follows: “We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.” Almost two centuries later, Ernst Mach (1838-1960), with his principle of economy, advocated a version of Ockham’s razor in stating: “Scientists must use the simplest means of arriving at their results and exclude everything not perceived by the senses”. Another re-statement of the principle is Morgan’s canon of parsimony introduced into comparative psychology. The principle is sometimes incorrectly equated with the statement purportedly made by Albert Einstein (1879-1955) in 1933 that “Theories should be as simple as possible, but no simpler”. It is often the case, however, that the simplest explanation is not necessarily the best. Finally, not everybody has regarded Ockam’s principle as a scientific mandate to be followed by all sciences. For example, Francis Crick (1916-2004) in an article entitled ‘Lessons from biology’, published in Natural History (November, 1988, pp. 32-39) wrote: “While Occam’s razor is a useful tool in the physical sciences, it can be a very dangerous implement in biology. It is thus very rash to use simplicity and elegance as a guide in biological research.”
See Akaike’s information criterion, Canon of parsimony, Experimental method, Operationalism, Reductionism