FACTS, PATENT AND OBSCURED 33 



known to him ; but, if he has the patience to read the rest of the 

 book, he will find that it was very necessary. In numbers of recent 

 publications the rules of ordinary scientific procedure have been 

 broken, and the breach, so far from being admitted as a fault, has 

 been claimed, explicitly or implicitly, as a merit. Even a cursory 

 consideration of scientific controversies renders it evident that the 

 fundamental source of almost every disagreement has been a 

 neglect, on one side or the other, to conform in practice with that 

 which in theory is regarded as a truism. Therefore, if we can 

 reach a preliminary agreement as to the materials for thought and 

 modes of thought which it is legitimate to employ, more than half 

 of the causes of disagreement will be eliminated at a stroke. At 

 this stage, for lack of illustrations with which to point the argu- 

 ment, the discussion will not be very complete. For example, I 

 shall find it impossible to demonstrate that masses of valuable 

 evidence, bearing on various great problems of heredity, have fre- 

 quently been ignored without valid excuse. But throughout the 

 remainder of the work I shall indicate illustrations as they arise. 



57. Some facts by far the greater number of facts known to 

 us are patent to our senses ; that is to say, we have only to look, 

 feel, hear, taste, smell, or invoke the muscular sense, and we become 

 aware of them. It is the function of our senses to supply us with 

 facts, and without them we could not maintain existence. But 

 other facts are of such a nature, or are so obscured by the settings 

 in which they occur, that they cannot be directly observed by our 

 senses, or inferred from the evidence supplied by them with any 

 degree of certainty. We have, then, to resort to experiment, 

 biometry, or some such ' laboratory ' method, to render, if possible, 

 these obscured facts as certainly known as those which are patent 

 from the first. When used for purposes of discovery, a laboratory 

 method is nothing other than a means of eliminating obscuring 

 conditions and so making hidden facts perceptible, or at least 

 capable of being inferred with greater certainty. " The object of 

 experiment is to eliminate unessential conditions in the phenomena ; 

 . . . when complete knowledge of the essential conditions can be 

 obtained by observation, experiment is unnecessary." * " Experi- 

 ment only has an advantage over observation, in so far as it is 

 capable of supplementing the usual deficiencies of the latter." 2 



58. The ascertained facts of some sciences, for example, 

 systematic zoology, botany, anatomy, and geology, are almost all 



1 Welton, Manual of Logic, vol. ii. p. 115. 



2 Lotze, Logic, Eng. Trans., vol. ii. p. 40. 



