THE LATEST STAGE 267 



obscurantism on the other, a nation that ignores the 

 survival value of religion, will perish from off the face 

 of the earth. 



Alongside the development of physical and biologi- 

 cal science which we have traced in the preceding 

 Theor of P a es > new attention has been devoted to 

 Scientific the fundamental concepts which lie at 

 Knowledge. the base of a]Q natural knowledge. Ernst 



Mach in Germany and Karl Pearson in England have 

 modified and developed the doctrines of Mill and 

 Herbert Spencer. 



In the laboratory, as in the practical life of the field 

 or the office, there is no time for philosophic doubt. 

 A naive realism is alone possible. We assume that 

 we know all about our spade or our pen, our test-tube 

 or our atom. Can we not see them, handle them, or, 

 at all events, trace their effects ? Yet if we think 

 carefully, we shall see that the case is not so simple as, 

 for practical convenience, unconsciously we assume. 



A spade is to our eyes a long-shaped figure of a 

 brown colour, tipped with a flat blade of grey. The 

 stored impressions of memory enable us to say it is of 

 wood and iron, and thereby to endow it with the 

 qualities we associate with those materials. We 

 construct a mental image of the spade, partly by 

 sense-impression, partly by an unconscious act of 

 memory. Our image is real, we can reason about it, 

 develop it by trying experiments and adding to our 

 ideas of wood and iron an idea of the complete spade 

 as an implement useful for digging, or, at a push, as 

 a weapon of offence. We are not conscious of our 

 mental process of synthesis ; we regard the spade as 



