vii THE TWO ORDERS in 



animal contacts and so forth. If we ask why man is left 

 without a power so useful, the answer can only be given 

 in very general terms. Negatively, the human body is not 

 the product of a finished design adapting it accurately to 

 all its needs. Positively, it is the development in all its 

 organs of a far ruder structure. By a ruthless elimination 

 of failures, the organs are rough-hewn and finally polished 

 down at certain points to an accurate adjustment to require- 

 ments. But nature makes no inventions like telephones 

 or microscopes. It works upon what is there, and in per- 

 fecting specialises it to one function, abandoning others. 

 If the human race can get along and survive with sight 

 adapted to our colour scale and to the sizes and distances 

 which we familiarly judge, that is enough for nature. The 

 fact that man would do infinitely better if with this he 

 could combine the eye of the telescope and the microscope 

 is nothing to her. For to drop the too ready metaphor of 

 personification, the physical structure is determined only 

 by the conditions of survival, not by the requirements of 

 an ideal type or a perfect economy. 



It is not only in its data but in its use of them that 

 ordinary thought betrays its origin. The common-sense 

 concept is a practically-useful concept, and as long as it 

 c works,' common sense cares little for criticism. The 

 c solidity ' of the table means that it will give you a nasty 

 bump if you run against it. That is definition enough 

 for the workaday world. The structural categories which 

 appear fundamental and tend to be used as sieves which 

 only let certain kinds of experience through into the 

 admitted tradition, are in fact products of certain elemen- 

 tary processes, which have been specified, working within 

 the empirical order. They are growths, and they have 

 arisen at the outset under fundamentally the same condi- 

 tions as those which we have traced in the rise of per- 

 ception. Only as human purposes develop and truth 

 becomes an object do more refined conditions come into 

 play ; of these conditions, and of their growth in general, 

 we shall have a word more to say at a later stage. For 

 the moment we may be content to note that whether we 

 look at its data or its methods, the whole structure of the 



