370 MIND IN EVOLUTION CHAP. 



But with this scepticism about fundamental conceptions, 

 we are thrown back on first principles. We shall need a 

 criterion of certainty, that is to say, a Logic. We shall 

 need an examination into the relation between the world 

 of our thought, and the world of ultimate reality, i.e., a 

 Metaphysic. And in these inquiries there is wrapped up 

 another which is, strictly speaking, a special science, but 

 yet is concerned with those mental processes which are at 

 work in building up science itself, i.e., Psychology. Clearly, 

 if we want to evaluate the human factor in human 

 thought, we must understand the laws of growth by which 

 our ways of thinking have arisen. Historically, therefore, 

 Psychology has arisen in close connection with Logic and 

 Metaphysics. This is not the place to argue the precise 

 delimitation of the spheres of Logic, Metaphysics, and 

 Psychology. What I have to do is to call attention to 

 the work which these three branches of investigation have 

 shared between themselves. This work has a double 

 aspect. On the one hand, it is essentially an analysis of 

 the work of mind, and to many people this would seem to 

 be the differentiating mark between philosophy and 

 science. Thus, if we wish to contrast the highest stage of 

 mental development with all those that have gone before, 

 we might say that while in all the other stages the mind is 

 at work correlating its experiences, in this stage for the 

 first time it turns to analysing the principle and method 

 of correlation itself, the laws that govern it in its system- 

 making. On the other hand it is only by evaluating this 

 unknown quantity that we get a determinate relation 

 between thought in any sphere, and reality. That is to 

 say, this analysis is the primary condition of a completed 

 synthesis. If the partial systems of science can be con- 

 ceivably built up into a unified science revealing the true 

 nature of things, this analysis must be the keystone of the 

 arch. 



4. This unification of experience is the ideal to which 

 philosophy points. For in the search for first principles, 

 philosophy finds itself brought up against something that 

 looks very like an insoluble contradiction. We cannot go 

 outside experience in order to j udge experience. We may 



