APPENDIX 5 37 



thought. It has been very concisely expressed by William of Occam 

 in the maxim : Entia noii sunt tnultiplicanda practer neccssitatem. 

 Sir William Hamilton in a valuable historical note {Discusszofis on 

 Philosophy^ 2nd. edition, pp. 628-31, London, 1853) quotes the 

 further scholastic axioms : Principia iron sunt cinnulanda and Fnist7-a 

 sit pc7- pliira quod fieri potest per pauciora. So far these axioms are 

 valuable as canons of thought, they express no dogma but a funda- 

 mental principle of the economy of thought. When, however. Sir 

 William Hamilton adds to them Natitra horret siiperfluiini, and says 

 that they only embody Aristotle's dicta that God and Nature never 

 operate superfluously and always through one rather than a plurality 

 of causes, then it seems to me we are passing from the safe field of 

 scientific thought to a region thickly strewn with the pitfalls of meta- 

 physical dogma. Aristotle and Newton's opinion that Natitra ettiin 

 simplex est is of the same character as Euler's Mundi iiniversi fabrica 

 eni/ii perfectissiina est. They either project the notions of " simple " 

 and " perfect " beyond the sphere of sense-impression, where alone 

 there is any meaning to the word knowledge, or else they confuse 

 the perceptual universe with man's scientific description of it. In the 

 latter field only is economy of principles and causes a true canon of 

 scientific thought. On this account the " law of parsimony," as Sir 

 William Hamilton has termed it, seems a product of scholastic 

 thought and not due to Aristotle. As stated by Occam, it is a far 

 more valid axiom than in Newton's version (p. 92), and I think it 

 might well be called after the Venerabilis Inceptor, who first recog- 

 nised that knowledge beyond the sphere of perception was only 

 another name for unreasoning faith. 



Sir William Hamilton expresses Occam's canon in the more com- 

 plete and adequate form : — 



Neither more, nor more onerous, causes are to be assumed, than are 

 7iecessary to account for the phenoinena. 



NOTE IV 



On the Vitality of Seeds (p. 338) 



The determination of the maximum period during which seeds will 

 maintain their vitality appears to be very far from settled. In the 

 first place, experiments lasting thirty, fifty, or one hundred years 

 cannot be rapidly executed,^ and secondly, well-authenticated cases of 

 the discovery of seeds several score years or even centuries old are 

 not very frequent. There seems, however, little doubt of seeds 

 preserving their power of germination for periods of forty to fifty and 

 even to one hundred and fifty years (British Association Report, 

 1850, p. 165 ; Darwin, Origin of Species, 4th edition, p. 430 ; Alph. 



1 Experiments are at present bein|, made at Kew with seeds buried in 

 bottles. 



