8 INTRODUCTORY [ch. 



Nevertheless, when philosophy bids us hearken and obey the 

 lessons both of mechanical and of teleological interpretation, the 

 precept is hard to follow: so that oftentimes it has come to pass, 

 just as in Bacon's day, that a leaning to the side of the final cause 

 "hath intercepted the severe and diligent enquiry of all real and 

 physical causes," and has brought it about that "the search of the 

 physical cause hath been neglected and passed in silence." So long 

 and so far as "fortuitous variation*" and the "survival of the 

 fittest" remain engrained as fundamental and satisfactory hypo- 

 theses in the philosophy of biology, so long will these "satisfactory 

 and specious causes" tend to stay "severe and diligent enquiry. . . 

 to the great arrest and prejudice of future discovery." Long 

 before the great Lord Keeper wrote these words, Roger Bacon had 

 shewn how easy it is, and how vain, to survey the operations of 

 Nature and idly refer her wondrous works to chance or accident, 

 or to the immediate interposition of Godf. 



The difiiculties which surround the concept of ultimate or "real" 

 caugation, in Bacon's or Newton's sense of the word, the in- 

 superable difficulty of giving any just and tenable account of the 

 relation of cause and effect from the empirical point of view, need 

 scarcely hinder us in our physical enquiry. As students of mathe- 

 matical and experimental physics we are content to deal with those 

 antecedents, or concomitants, of our phenomena without which the 

 phenomenon does not occur — with causes, in short, which, aliae ex 

 aliis aptaetet necessitate' nexae, are no more, and no less, than con- 

 ditions sine qua non. Our purpose is still adequately . fulfilled : 

 inasmuch as we are still enabled to correlate, and to equate, our 

 particular phenomena with more and more of the physical phenomena 

 around, and so to weave a web of connection and interdependence 

 which shall serve our turn, though the metaphysician withhold from 

 that interdependence the title of causality J. We come in touch 



* The reader will understand that I speak, not of the "severe and diligent 

 enquiry" of variation or of fortuity, but merely of the easy assumption that these 

 phenomena are a sufficient basis on which to rest, with the all-powerful help of 

 natural selection, a theory of definite and progressive evolution. 



f Op. tert. (ed. Brewer, p. 99). "Ideo mirabiles actiones naturae, quae tota 

 die fiunt in nobis et in rebus coram oculis nostris, non percipimus; sed aestimamus 

 eas fieri vel per specialem operationem divinam. . .vel a casu et fortuna," 



t Cf. Fourier's phrase, in his Theorie de la Chaleur, with which Thomson and 

 Tait prefaced their Treatise an Natural Philosophy: "Les causes primordiales ne 



