The Evolution Hypothesis. 



assuring ourselves that the whole fact has been 

 for our purpose discovered. It' all nature form one 

 cosmos, as the scientist assumes, the whole is joined 

 together in a real unity, so that no one part is separ- 

 able from any other part. Each instance is in effect 

 the entire universe. Every object of inquiry thus 

 extends immeasurably beyond the limits of possible 

 experience ; and that vast unknown is as essential to 

 the instance before us as that in it which may be 

 brought within the field of vision. We may suffi- 

 ciently understand the phenomenon, and its relations 

 within the visible, to reach conclusions that will be 

 valid within experience ; but we should need to ex- 

 haust every relation in which the object stands to 

 every other mode of existence in the cosmos, before 

 we could reason with confidence from the instance 

 and its law to the limitless totality of things. Such 

 completeness of knowledge is not given to man. The 

 scientific inquirer must always remain in the attitude 

 of expectance, willing to modify his doctrine should 

 any new phase of the phenomena under investigation 

 be presented. There are laws, within their proper 

 limits, well-established and sure: but when the 

 physicist carries them beyond the bounds of ex- 

 perience he is always beset by doubt ; he cannot 

 reason with the full assurance of one who deals with 

 universal and necessary truth. 



When, therefore, an hypothesis is framed to cover 

 the whole extent of knowable existence, and is based 



