152 PRESENT-DAY RATIONALISM 



means of [indefinite variations of structure and] Natural Selec- 

 tion," is not "the doctrine of Malthus applied with manifold 

 force to the whole animal and vegetable kingdoms. As many 

 more individuals of each species are born than can possibly 

 survive ... it follows that any being, if it vary however 

 slightly in any manner profitable to itself, under the complex 

 and sometimes varying conditions of life, will have a better 

 chance of surviving, and thus be naturally selected. From the 

 strong principle of inheritance any selected variety will tend to 

 propagate its new and modified form."^ 



I have italicised the unwarranted intercalation into Malthus' 

 theory. 



The mistake Darwin here makes is to suppose that life and 

 death depend upon slight changes of Structure ; whereas they 

 are far more concerned with constitution, which has nothing to 

 do with the origination of changes of Form. 



In the case of plants growing thickly together, the strongest 

 plants survive by crowding out the weaker. 



Darwin very often alludes incidentally to " constitution," 

 as a factor in the struggle for life; but it has nothing to do 

 with the origin of new " variations of structure," upon which 

 alone new varieties are formed. I must repeat this, to make it 

 emphatic. 



Of course, if it could be proved that new variations of 

 structure and form are in any way or always in correlation with 

 an enhanced vigorous constitution, there might be a shadow of 

 support to his theory ; but there is nothing to say for such 

 correlation as necessarily occurring. Hence, Darwin's applica- 

 tion of Malthus' theory to variations is an illegitimate one ; 

 for it will in no way account for them : nor when they arise 

 does it explain why they should survive. The transferring the 

 struggle for life from the constitution to variation is an 

 illegitimate procedure. 



Now let us see what Darwin has to say about Natural 

 Selection. I have mentioned that as long as animals and 



' Origin of Species, p. 3. 



