To Adam Sedgwick 26 November 
Ilkley Wells House | Otley, Yorkshire
My dear Prof. Sedgwick
I did not at all expect that you would have written to me.—1 You could not possibly have paid me a more honourable compliment than in expressing freely your strong disapprobation of my Book.— I fully expected it. I can only say that I have worked like a slave on the subject for above 20 years & am not conscious that bad motives have influenced the conclusions at which I have arrived. I grieve to have shocked a man whom I sincerely honour. But I do not think you would wish anyone to conceal the results at which he has arrived after he has worked, according to the best ability which may be in him. I do not think my book will be mischievous; for there are so many workers that, if I be wrong I shall soon be annihilated; & surely you will agree that truth can be known only by rising victorious from every attack.
I daresay I may have written too confidently from feeling so confident of the truth of my main doctrine. I have made already a few converts of good & tried naturalists & oddly enough two of them compliment me on my cautious mode of expression! This will make you laugh. My notion of young men being best judges of new doctrines was not invented for occasion; for however erroneous, I remember nearly twenty years ago laughing with Lyell over the idea.— I have tried to be honest in giving all the many & grave difficulties which occurred to me, or I met in published works. I cannot think a false theory would explain so many classes of facts, as the theory seems to me to do. But magna est veritas & thank God, prevalebit.
Forgive me for scribbling at such length, & let me say again how I grieved I am to have encountered your severe disapprobation & ridicule. Your kind & noble heart shows itself througout your letter. I thank you for writing, & remain with sincere respect | Yours truly obliged | Charles Darwin
CD expected AS’s "strong disapprobation" of his book [Origin] but is grieved "to have shocked a man whom I sincerely honour". Has worked "like a slave" on the subject for over 20 years and is not conscious that bad motives have influenced the conclusions at which he has arrived. CD does not think the book will be mischievous and "if I be wrong I shall soon be annihilated". CD may have written too confidently from feeling confident that no "false theory would explain so many classes of facts".