From Emma Darwin [c. February 1839]1
The state of mind that I wish to preserve with respect to you, is to feel that while you are acting conscientiously & sincerely wishing, & trying to learn the truth, you cannot be wrong; but there are some reasons that force themselves upon me & prevent my being always able to give myself this comfort. I dare say you have often thought of them before, but I will write down what has been in my head, knowing that my own dearest will indulge me. Your mind & time are full of the most interesting subjects & thoughts of the most absorbing kind, viz following up yr own discoveries—but which make it very difficult for you to avoid casting out as interruptions other sorts of thoughts which have no relation to what you are pursuing or to to be able to give your whole attention to both sides of the question.
There is another reason which would have a great effect on a woman, but I don’t know whether it wd so much on a man— I mean E. whose understanding you have such a very high opinion of & whom you have so much affection for, having gone before you—2 is it not likely to have made it easier to you & to have taken off some of that dread & fear which the feeling of doubting first gives & which I do not think an unreasonable or superstitious feeling. It seems to me also that the line of your pursuits may have led you to view chiefly the difficulties on one side, & that you have not had time to consider & study the chain of difficulties on the other, but I believe you do not consider your opinion as formed. May not the habit in scientific pursuits of believing nothing till it is proved, influence your mind too much in other things which cannot be proved in the same way, & which if true are likely to be above our comprehension. I should say also that there is a danger in giving up revelation which does not exist on the other side, that is the fear of ingratitude in casting off what has been done for your benefit as well as for that of all the world & which ought to make you still more careful, perhaps even fearful lest you should not have taken all the pains you could to judge truly. I do not know whether this is arguing as if one side were true & the other false, which I meant to avoid, but I think not. I do not quite agree with you in what you once said—that luckily there were no doubts as to how one ought to act. I think prayer is an instance to the contrary, in one case it is a positive duty & perhaps not in the other. But I dare say you meant in actions which concern others & then I agree with you almost if not quite. I do not wish for any answer to all this—it is a satisfaction to me to write it & when I talk to you about it I cannot say exactly what I wish to say, & I know you will have patience, with your own dear wife. Don’t think that it is not my affair & that it does not much signify to me. Every thing that concerns you concerns me & I should be most unhappy if I thought we did not belong to each other forever
I am rather afraid my own dear Nigger will think I have forgotten my promise not to bother him, but I am sure he loves me & I cannot tell him how happy he makes me & how dearly I love him & thank him for all his affection which makes the happiness of my life more & more every day.
Discusses CD’s religious doubts. Fears his work may lead him to discount what cannot be proved, and advises that there are some things which, "if true are likely to be above our comprehension" and "that there is a danger in giving up revelation".