THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 63 



theory upon the concept of a " displacement " to which it is 

 impossible to assign a definite meaning,* while Lord Kelvin, 

 speaking on the same subject said, " As long as I cannot make 

 a mechanical model all the way through, I cannot understand, 

 and that is why I cannot get the electro-magnetic theory 

 of light."f An almost better illustration is afforded by 

 Dr. McBougall, who not only conceives his " neurin " as a fluid, 

 but defends his practice in an excellent notej by arguments 

 essentially the same as those I am advancing. Finally, it is 

 clear, that this doctrine of the relation of the scientific concept 

 to the primary facts does not exclude the concept of "end" 

 from the investigator's armoury of interpretative weapons and 

 so admits the methodological propriety of the practice of 

 " neo-vitalists " such as Bunge and Eindefleisch. Our doctrine, 

 moreover, has a normative value. It declares that a concept 

 which is to render given primary facts intelligible must be formed 

 as a reaction upon the stimulus of the presentation of those 

 facts in their actual determinations. While it admits, then, 

 the aid of any concept borrowed from any other context, it 

 refuses to allow Objective facts to be annexed simply in order 

 to widen the territories of an aggressive theory, and still less to 

 permit their primd facie deliverances to be ignored through a 

 bias in favour of any particular type of interpretation. Thus 

 " electricity " and " neurin " may both be legitimately conceived 

 as fluids, but the physicist is not to rule the concept of 

 " interaction" or of a " soul" out of court, and still less is he 

 to refuse to entertain evidence in favour of " telepathy. "|| 



The only restriction upon the secondary construction is that 

 its form shall be determined by the actual particulars of the 



* See Merz, Op. ciL, ii, 93. 



t Quoted by Ward, Naturalism and Agnosticism, i, p. 119. 



| McDougall, "The Physiological Factors of the Attention Process," 

 Mind, N.S., No. 43, p. 350. 



Cf. James, Pr. of Psych., i, p. 137 ; McDougall, Physiological 

 Psychology, pp. 8 et seq., p. 78. 



|| As at least one very distinguished scientist is reported to have done. 



