After reading Darwin’s Origin, Adam Sedgwick, Darwin’s professor of natural science when he attended the University of Cambridge, wrote Darwin to express deep concerns about the theory:
There is a moral or metaphysical part of nature as well as a physical. A man who denies this is deep in the mire of folly. Tis the crown and glory of organic science that it does, through final cause, link material to moral; & yet does not allow us to mingle them in our first conception of laws, and our classification of such laws whether we consider one side of nature or the other. You have ignored this link; and, if I do not mistake your meaning, you have done your best in one or two pregnant cases to break it. Were it possible (which, thank God, it is not) to break it, humanity, in my mind would suffer a damage that might brutalized it, and sink the human race into a lower grade of degradation than any into which it has fallen since its written records tell us of its history.
Stunned by Sedgwick’s response, Darwin protested, “I do not think my book will be mischievous.” See below.
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