THE METHOD OF SCIENCE 55 



of facts in accordance with certain basic ideas that may be 

 termed the postulates. It is necessary that these postulates 

 should be logical and that they should be clear in the sense 

 that they can be reasoned about. Moreover, in scientific 

 work stress is laid on the simplicity of the postulates and on 

 the postulates being as few in number as possible. The 

 simplicity rule is always applied when a choice must be made 

 between two theories. Newton says: "Nature is pleased with 

 simplicity." * This is so well recognized in scientific work 

 that there are classic statements of the rules of systematic 

 inquiry. William of Occam, the English philosopher of the 

 fourteenth century, expressed it in a phrase which is known 

 as ''Occam's razor." In Hamilton's translation, it is: "Neither 

 more, nor more onerous causes are to be assumed than are 

 necessary to account for the phenomena." Newton's version 

 in his Rules of Philosophizing reads: "No more causes of 

 natural things are to be admitted than such as are both true 

 and sufficient to explain the phenomena of these things." 



In practice, this demand for simplicity competes with the 

 further requirements that the theory shall fit as many types 

 of fact as possible. The very simple rule that Robert Boyle 

 gave for the relation between the volume and the pressure of 

 a gas holds for only a limited range of pressures. In order to 

 cover a wider range, it must be complicated by the addition 

 of the term suggested by van der Waals. 



George points out that, provided the postulates of a theory 

 are sound, it does not matter if they appear absurd or con- 

 trary to common sense. Almost everything new appears ab- 

 surd. Absurdity is associated primarily with the unusual. 

 The headdress of a Zulu rickshaw man does not appear ab- 

 surd to a resident of Durban, but it would excite a great deal 

 of interest and amusement in San Francisco. And the story 

 of the ridicule excited by the first umbrella should warn us 

 against regarding the appearance of absurdity as having any 

 relation to value. Both the quantum theory of Planck and 



* George, op. cit., p. 240. 



