100 A Modal Formula 



that uncertainty in regard to the factors cannot be 

 said to affect the validity of the modal concept of 

 evolution, and it is entirely unfair to use confessions 

 of ignorance in regard to the factors as if they im- 

 plied doubt in regard to the fact. One authority de- 

 clares that the Domestic Cat originated from the 

 Caffre Cat of Egypt ; another says that it is a scion 

 of the European Wild Cat species ; a third maintains 

 a multiple origin ; and none of the three can describe 

 the actual steps in the transformation. But all are 

 agreed that the Domestic Cats have evolved from 

 wild ancestors. We must recognize how young active 

 evolutionist inquiry is, that it is practically included 

 in two generations. There is not the slightest reason 

 for jettisoning the modal formula because we are 

 still very ignorant in regard to the detailed steps and 

 factors in the process. 



It may be urged, however, that a modal formula is 

 unsatisfactory until it is supported by a causal de- 

 scription ; and that is true. It is possible that besides 

 variation and heredity, selection and isolation, there 

 may be some unknown factor in organic evolution. 

 And this raises the question whether the unknown 

 factor may not be of a providential order, some super- 

 mundane directive agency intervening at crises. This 

 was the view of Alfred Russel Wallace, Darwin's 

 magnanimous fellow-worker ; we can only say that it 

 seems to us to imply a premature abandonment of 

 the scientific problem, and that it lands us in the con- 

 fusion of trying to speak two languages at once. 



