300 CAUSATION 



limits of these gross appliances; so that it is a truism 

 with a probable error — small, but not infinitely small. 

 The classical laws hold good in the limit when exceed- 

 ingly large quantum numbers are involved. The system 

 comprising the sun, earth and moon has exceedingly 

 high state-number (p. 198); and the predictability of 

 its configurations is not characteristic of natural pheno- 

 mena in general but of those involving great numbers 

 of atoms of action — such that we are concerned not 

 with individual but with average behaviour. 



Human life is proverbially uncertain; few things are 

 more certain than the solvency of a life-insurance com- 

 pany. The average law is so trustworthy that it may be 

 considered predestined that half the children now born 

 will survive the age of x years. But that does not tell us 

 whether the span of life of young A. McB. is already 

 written in the book of fate, or whether there is still time 

 to alter it by teaching him not to run in front of motor- 

 buses. The eclipse in 1999 is as safe as the balance of 

 a life-insurance company; the next quantum jump of an 

 atom is as uncertain as your life and mine. 



We are thus in a position to answer the main argu- 

 ment for a predetermination of the future, viz. that 

 observation shows the laws of Nature to be of a type 

 which leads to definite predictions of the future, and it 

 is reasonable to expect that any laws which remain 

 undiscovered will conform to the same type. For when 

 we ask what is the characteristic of the phenomena that 

 have been successfully predicted, the answer is that they 

 are effects depending on the average configurations of vast 

 numbers of individual entities. But averages are pre- 

 dictable because they are averages, irrespective of the 

 type of government of the phenomena underlying 

 them. 



