ii.l THE PLANT AND THE ANIMAL 105 



the contrary, the portals of the future remain wide open. 

 It is a creation that goes on for ever in virtue of an initial 

 movement. This movement constitutes the unity of 

 the organized world — a prolific unity, of an infinite rich- 

 ness, superior to any that the intellect could dream of, 

 for the intellect is only one of its aspects or products. 



But it is easier to define the method than to apply it. 

 The complete interpretation of the evolution movement 

 in the past, as we conceive it, would be possible only if 

 the history of the development of the organized world 

 were entirely known. Such is far from being the case. 

 The genealogies proposed for the different species are 

 generally questionable. They vary with their authors, 

 with the theoretic views inspiring them, and raise dis- 

 cussions to which the present state of science does not 

 admit of a final settlement. But a comparison of the 

 different solutions shows that the controversy bears less 

 on the main lines of the movement than on matters of detail ; 

 and so, by following the main lines as closely as possible, 

 we shall be sure of not going astray. Moreover, they alone 

 are important to us; for we do not aim, like the naturalist, 

 at finding the order of succession of different species, but 

 only at defining the principal directions of their evolution. 

 And not all of these directions have the same interest for 

 us: what concerns us particularly is the path that leads 

 to man. We shall therefore not lose sight of the fact, 

 in following one direction and another, that our main 

 business is to determine the relation of man to the animal 

 kingdom, and the place of the animal kingdom itself in the 

 organized world as a whole. 



To begin with the second point, let us say that no definite 

 characteristic distinguishes the plant from the animal. 

 Attempts to define the two kingdoms strictly have always 



