LIFE 



355 



compare them, forms the sole basis of our assertion that 

 the model can be used to describe the non-perceptible 

 past and future. If two curves were to be in contact 

 along the whole of that portion of the arc which we were 

 capable of examining, it would be valid to replace one 

 curve by the other ; and to calculate the probability that 

 the curves would continue to touch, would be to measure 

 the belief we ought to put in our scientific predictions as 

 to the future (p. 148). The capacity of the conceptual 

 curve for representing the phenomenal curve within the 

 sphere of our perceptions would not be in the least 



^■'onceptualBesc?^^ 



.,a-c ofTI'ciwmata 



Fig. 25. 



invalidated if the phenomenal curve came to a full stop 

 beyond the sphere of perception.^ 



It is only when the symbols of our conceptual de- 

 scription are treated as the substrata of perception, or 

 converted into what may truly be described as " ultra- 

 scientific causes " of the routine of phenomena, it is only 

 when the scientist becomes metaphysical, that difficulty 

 arises. In biology this projection seems invariably to 

 occur through the channel of physics ; the biologist looks 

 to force, chemical constitution, molecular structure, for an 

 explanation, where at best they can merely provide con- 

 ceptual shorthand for descriptive purposes. It seems all 

 the more necessary to emphasise and repeat this important 

 distinction, because the failure to grasp it has been made 



1 The analogy to the laws of science may be still better brought home, at 

 least to the mathematician, by supposing the equation to the conceptual curve 

 known, but not that to the fragment of a curve AB (Fig. 25). The singular 

 points A and B would not lend themselves to scientific description, they would 

 fall outside the field of possible knowledge. 



