ii SCIENTIFIC RECONSTRUCTION 273 



and the senses of sight, touch and hearing supply us with 

 information about outer objects which in the mass corro- 

 borate one another. The coherence, however, is not 

 complete. The abnormal plays its part, and there are 

 departments of the environment, like the weather, where 

 mutability reigns. The lack of completeness leaves an 

 element of uncertainty in the domain of common sense, 

 and forces the candid to acquiesce in the judgment that, 

 after all, probability is the rule of life. The endeavour 

 towards a more complete, and also a more express and 

 conscious coherence, takes us into the region of science 

 and of philosophy. Here the true character of coherence 

 tends to be masked by the impulse to find a single first 

 principle from which a department of truth or perhaps (in 

 philosophy) the whole of truth may be deductively inferred. 

 This impulse is in reality due to a one-sided apprehension 

 of the idea of systematic unity. What appear as 'first' 

 principles are, in fact, based on the harmony of experience 

 which they themselves reveal. They are neither a priori 

 truths nor mere assumptions which turn out to be consistent 

 with experience. They express the pervading unity in a 

 system of judgments shown, in the manner indicated above, 

 to necessitate one another, and such a system we now see is 

 precisely what we mean by a rational and valid body of 

 thought. 



We have now seen in what sense it is possible to meet 

 the demand that a reason shall be given for all that we 

 think. It remains to consider why and in what sense it is 

 irrational to let our thoughts be determined by our desires, 

 emotions, or, in fact, by anything proceeding from our own 

 peculiar mental make-up rather than the intrinsic character 

 and relations /of the objects asserted. The most obvious 

 objection to this element in our definition of the irrational 

 is that reason itself our connected system of judgments 

 will force us to recognise facts which depend for their bare 

 existence on c our own peculiar mental make-up.' Any 

 fact of my own consciousness, any feeling or emotion, for 

 instance, comes into being because I am so constituted as to 

 feel it. There may be an c external ' exciting cause, but the 

 feeling is the reaction of the conscious being upon it, and 



s 



