26 The Evolution Hypothesis. 



clearest form : Knowledge of the lowest kind is un- 

 unified knowledge; Science is partially - unified 

 knowledge ; Philosophy is completely -unified know- 

 ledge." * 



Mr. Spencer's system is framed of such " universal 

 propositions " derived from generalizations of science 

 beginning " with a mere colligation of crude observa- 

 tions." Do these generalizations furnish truths which 

 may be turned into universals holding good over the 

 whole universe of being, and dominating all thought ? 

 They do not. The truths of experiential science cannot 

 be so used legitimately : and the philosophy founded 

 on such a basis is demonstrably false. 



To make this position clear it is necessary to inquire 

 into the limits of physical science. The physicist 

 may not add anything to nature : it is his business to 

 |see what is, and nothing but what is. His science is 

 strictly bounded by observation, and can speak only in 

 the name of known facts, and of such facts as are, in 

 the points of comparison, precisely similar. Physical 

 science is imperatively enclosed within the actually 

 known. Where it deals with that which is not 

 actually known, it must invariably carry forward into 

 the unknown that which is known, and with the 

 assumption that the conditions, so far as affects the 

 matter dealt with, are identical. Given other con- 

 ditions, and the result will be different. Science may 



* First Principles, 37. 



