THE CLASSIFICATION OF THE SCIENCES 505 



scientific thought, which probably has for its physical 

 aspect the development or establishment of what the 

 physiologist would term " commissural " links between the 

 physical centres of thought.^ 



To recognise that the contents of the mind thus ulti- 

 mately take their origin in sense-impressions, and in our 

 modes of perceiving sense-impressions, may indeed limit 

 the material which we have to classify, by removing, for 

 example, natural theology and metaphysics from the field 

 of knowledge ; but it still does not render the task of 

 classifying the various departments of science an easy one. 

 Indeed, as soon as we approach any definite range ot 

 perceptual experience, we feel at once the need of a 

 specialist to tell us " the lie of the land " — to describe to 

 us how it is related to surrounding districts and what are 

 the exact bearings of the corresponding branch of science 

 on other problems of life and mind. The development of 

 the embryo before birth may be a reproduction in minia- 

 ture of the evolution of the species ; the changes of minute 

 microscopic organisms may be crucial for theories of 

 heredity or of disease which involve momentous results 

 for sociology ; the mathematician carried along on his 

 flood of symbols, dealing apparently with purely formal 

 truths, may still reach results of endless importance for 

 our description of the physical universe. Such possibilities 

 suffice to show how incapable any individual scientist 

 must nowadays be of truly measuring the importance of 

 each separate branch of science and of seeing its relation 

 to the whole of human knowledge. An adequate classifi- 

 cation could only be reached by a group of scientists 

 having a wide appreciation of each other's fields, and a 

 thorough knowledge of their own branches of learning. 

 They must further be endowed with sympathy and patience 

 enough to work out a scheme in combination. Their 

 labours would, indeed, in course of time, come to have 



' The extent to which the localisation of the centres of thought or of the 

 different elements of consciousness has aheady proceeded would be brought 

 home to the reader by even a cursory inspection of H. C. Bastian : 77^1? 

 Brain as an Organ of Mind (pp. 477-700) ; or J- Ross : On Aphasia 

 (especially pp. 87-127). 



