144 THE WRITING OF THE 'ORIGIN OF SPECIES.' [1859. 



C Darwin to J. D. Hooker. 



Down, Jan. 2oth, 1859. 



MY DEAR HOOKER, I should very much like to borrow 

 Heer at some future time, for I want to read nothing per- 

 plexing at present till my Abstract is done. Your last very 

 instructive letter shall make me very cautious on the hyper- 

 speculative points we have been discussing. 



When you say you cannot master the train of thoughts, 

 I know well enough that they are too doubtful and obscure to 

 be mastered. I have often experienced what you call the 

 humiliating feeling of getting more and more involved in 

 doubt, the more one thinks of the facts and reasoning on 

 doubtful points. But I always comfort myself with thinking 

 of the future, and in the full belief that the problems which we 

 are just entering on, will some day be solved ; and if we just 

 break the ground we shall have done some service, even if we 

 reap no harvest. 



I quite agree that we only differ in degree about the means 

 of dispersal, and that I think a satisfactory amount of accord- 

 ance. You put in a very striking manner the mutation of our 

 continents, and I quite agree ; I doubt only about our oceans. 



I also agree (I am in a very agreeing frame of mind) with 

 your argumentum ad hominem, about the highness of the 

 Australian Flora from the number of species and genera ; but 

 here comes in a superlative bothering element of doubt, viz. 

 the effects of isolation. 



The only point in which I presumptuously rather demur 

 is about the status of the naturalised plants in Australia. I 

 think Miiller speaks of their having spread largely beyond 

 cultivated ground ; and I can hardly believe that our Euro- 

 pean plants would occupy stations so barren that the native 

 plants could not live there. I should require much evidence 

 to make me believe this. I have written this note merely to 

 thank you, as you will see it requires no answer. 



