Perhaps the most notorious realm of controversy over evolution in Darwin's day was religion. The same can be said of the evolution controversy today; however the nature of the disputes and the manner in which they were conducted in the nineteenth century were different in important ways. Many of Darwin's leading supporters were Christian, and found various ways of reconciling their religious beliefs with evolutionary theory. Darwin's own writing, both in print and letters, facilitated this reconciliation to some degree, although he tended to avoid the subject as much as possible. A number of correspondents tried to draw Darwin out on his own religious views, and the implications of his theory for religion in general. Darwin's name was also appropriated by secularists, materialists, and aggressive critics of institutional Christianity, so that the relationship between Darwinism and religion was extremely variable in different national and political contexts.
Darwin was not the first to challenge theological/natural design, nor is it clear that by challenging design, he provided a position completely incompatible with all forms of natural theology popular at the time. The following three sets of letters offer different perspectives on the controversial topic of design. The first is between Darwin and Harvard botanist Asa Gray, taking as their point of departure reviews of Origin. The second is a single letter from naturalist A. R. Wallace to Darwin on design and natural selection. The third is a single letter from Darwin to philosopher and economist William Graham on natural laws.
Darwin and Gray
Letter 2814 — Darwin, C. R. to Gray, Asa, 22 May 
Darwin writes to Gray about the opinions and reviews of Origin. He also shares his view on design in nature. Although he does not believe in the necessity of design, he finds it hard to conclude that everything is the result of “brute force”.
Letter 2855 — Darwin, C. R. to Gray, Asa, 3 July 
Darwin writes to Gray and tells him Origin has “stirred up the mud with a vengeance”; Gray and three or four others have saved him from annihilation and are responsible for the attention now given to the subject. He poses Gray a question on design in nature, as he is in a “muddle” on this issue.
Letter 3256 — Darwin, C. R. to Gray, Asa, 17 Sept 
Darwin writes to Gray about botany and his botanical experiments. He also discusses his views on design. He shares a witty thought experiment about an angel.
Letter 3342 — Darwin, C. R. to Gray, Asa, 11 Dec 
Darwin writes to Gray about politics and his forthcoming botanical papers. He says he is in a “thick mud” regarding design in nature, and more inclined to “show a white flag than to fire my usual long-range shot”. He asks Gray some questions about design.
Letter 6167 — Darwin, C. R. to Gray, Asa, 8 May 
Darwin writes to Gray about his review of Variation [Nation 6 (1868): 234–6] which he thinks is very good. Darwin also thinks he gives an “excellent idea of Pangenesis”. He talks about Gray giving him a good slap at his concluding paragraph, where he ought to have brought in and contrasted natural and artificial selection. He says that it seemed so obvious that natural selection depended on contingencies even more complex than those which must have “determined the shape of each fragment at the base of my precipice”.
Darwin and Wallace
Letter 5140 — Wallace, A. R. to Darwin, C. R., 2 July 1866
Wallace writes a lengthy analysis of sources of misunderstanding of natural selection. He worries about the accusation in Darwin & his teachings “Natural Selection" requires the constant watching of an intelligent ‘chooser’ like man's selection to which you so often compare it.” He discusses the advocacy of Spencer’s term “survival of the fittest” instead of “Natural Selection”. Wallace urges Darwin to stress frequency of variations.
Darwin and Graham
Letter 13230 — Darwin, C. R. to Graham, William, 3 July 1881
Darwin praises Graham’s Creed of science, but disagrees that the existence of natural laws implies purpose. His “inmost conviction” is that “the Universe is not the result of chance” but has horrid doubt whether convictions of man’s mind, which has been developed from lower animals, are at all trustworthy. He also believes natural selection is doing more for progress of civilisation than Graham admits.
This collection of letters explores Darwin’s reluctance to take a definitive position on the nature of God through correspondence with a variety of people, including members of his own family.
Letter 441 — Wedgwood, Emma to Darwin, C. R., [21–22 Nov 1838]
In this letter, his soon-to-be wife, Emma, writes lovingly to Darwin of small events since he left Maer. She fears their opinions may differ on “the most important subject”, religion, but is grateful for his openness about his “honest & conscientious doubts”.
Letter 471 — Darwin, Emma to Darwin, C. R., [c. Feb 1839]
Emma discusses Darwin’s religious doubts. She 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”.
Letter 2534 — Kingsley, Charles to Darwin, C. R., 18 Nov 1859
Clergyman Charles Kingsley judges Darwin’s book [Origin] free from two superstitions: the dogma of the permanent species and the need of an act of intervention to bring change.
Letter 2548 — Sedgwick, Adam to Darwin, C. R., 24 Nov 1859
Woodwardian Professor of geology, Adam Sedgwick thanks Darwin for the Origin; but has read the book “with more pain than pleasure”. He talks about his dislike of the conclusion of the book and how he instead “humbly accepts God’s revelation of himself both in His works & in His word; & will do my best to act in conformity with that knowledge which only He can give me.”
Letter 5303 — Boole, M. E. to Darwin, C. R., 13 Dec 1866
In this letter marked “private”, mathematician and teacher Mary Boole asks whether Darwin believes natural selection obviates man’s ability to be guided by spiritual motives. She is anxious that his theory be compatible with her faith.
Letter 5307 — Darwin, C. R. to Boole, M. E., 14 Dec 1866
Darwin believes he is unable to answer Mary Boole’s questions about religious implications of natural selection, but would prefer to believe that suffering in world is due to natural events. In the postscript, he feels that theology and science should each run its own course.
Letter 8070 — Darwin, C. R. to Abbot, F. E., 16 Nov 
Darwin explains why he must decline to write for the Index: his health is poor and he has never systematically thought much on religion. He says Abbot may print his comments, “with qualifications”, if he wishes.
Letter 8837 — Darwin, C. R. to Doedes, N. D., 2 Apr 1873
Darwin explains the impossibility of conceiving that the universe arose through chance is the chief argument for the existence of God, but Darwin has never been able to decide whether this is an argument of real value. He thinks it is safest to believe that the subject is beyond man’s intellect, “but man can do his duty”.
Letter 12041 — Darwin, C. R. to Fordyce, John, 7 May 1879
In this letter marked “private”, Darwin says to John Fordyce that he believes it is absurd to doubt that a man may be an ardent theist and evolutionist, giving the examples of Kingsley and Asa Gray. As regards his own views, his judgement often fluctuates but “I have never been an Atheist in the sense of denying the existence of God”. He thinks that “generally (and more and more as I grow older) … an Agnostic would be the most correct description of my state of mind”.
Letter 12757 — Darwin, C. R. to Aveling, E. B., 13 Oct 1880
In this letter marked “private”, Darwin says to Physician E. B. Aveling that the publication of Aveling’s remarks on his writings requires no consent on his part. Darwin would prefer that no part or volume be dedicated to him as it would imply his general approval of the publication, of which he knows nothing. Though he is a strong advocate of free-thought, Darwin feels that direct attacks on Christianity and theism produce hardly any effect. Freedom of thought is best promoted by gradual illumination of men’s minds produced by advance of science. He has therefore avoided writing on religion but states “I may have been unduly biassed by the pain which it would give members of my family, if I aided in any way direct attacks on religion”.
Darwin wrote to many people on his account of beauty. In this collection of letters, written after the Duke of Argyll’s address to the Royal Society of Edinburgh (1864), Darwin used birds, flowers and butterflies as examples to illustrate his ideas on beauty.
Letter 4752 — Darwin, C. R. to Lyell, Charles, 22 Jan 
Darwin writes to King's College, London Professor of geology, Charles Lyell, criticising the Duke of Argyll’s address [to the Royal Society of Edinburgh (1864)] on beauty and sexual selection. He discusses humming birds and orchids as examples.
Letter 4939 — Shaw, James to Darwin, C. R., 20 Nov 1865
Scottish school teacher and writer James Shaw praises Darwin’s theory. He believes beauty in nature is caused by sexual selection, but there is quite a long discussion on beauty in the natural world.
Letter 4943 — Darwin, C. R. to Shaw, James, 30 Nov 1865
Darwin writes to James Shaw. He is gratified that Shaw defends views of Origin. He thinks beauty of flowers is solely to attract insects.
Letter 5003f — Shaw, James to Darwin, C. R., [6--10 Feb 1866]
James Shaw transcribes a newspaper report of the paper he read to the Dumfriesshire and Galloway Natural History and Antiquarian Society on 6 February. In it Shaw defends Darwin’s account of Beauty against the Duke of Argyll’s criticisms.
Letter 5004 — Darwin, C. R. to Shaw, James, 11 Feb 
Darwin thanks James Shaw for the abstract of his paper on beauty. He discusses beauty of birds and butterflies, noting in particular that butterflies offer an excellent instance of beauty being displayed in conspicuous parts.
Letter 5060 — Shaw, James to Darwin, C. R., 19 Apr 1866
James Shaw fills a letter to Darwin with anecdotes about appreciation of beauty by animals.
Letter 5565 — Kingsley, Charles to Darwin, C. R., 6 June 1867
Clergyman Charles Kingsley writes to Darwin criticising the Duke of Argyll’s book [Reign of law (1867)], particularly on beauty and sexual selection. However, he believes Darwin overlooks God’s intention to instruct man by nature’s beauty.
Letter 5648 — Darwin, C. R. to Wallace, A. R., 12–13 Oct 
Darwin thinks naturalist A. R. Wallace’s remarks on hideous objects and on flowers not being made beautiful except when of practical use to them are good. He thinks the Duke of Argyll’s argument on beauty is not candid.
Darwin played an active role in the affairs of St Mary's Church at Down village. The following three letter sets provide a glimpse of church life and Darwin’s part in it, from future plans regarding the church, to the relationship between the church and school at Down, to the scandalous departure of S. J. H. Horsman, Down’s Curate.
Letter 182 — Darwin, E. A. to Darwin, C. R., 18 Aug 
Darwin’s brother Erasmus A. Darwin reports on the commissions Darwin requested of him [in a missing letter], comments on English political issues, and family gossip. He responds to a comment Darwin made in a missing letter about his future plans regarding the Church.
Letter 297 — Darwin, S. E. to Darwin, C. R., 12 Feb 1836
Darwin’s sister Sarah E. Darwin reports on the commissions Darwin requested of her [in a missing letter], comments on English political issues and family gossip. As was the case in an earlier letter from her brother Erasmus to Darwin, she too wonders about Darwin’s future plans with respect to the Church.
Church and School
Letter 1536 — Darwin, C. R. to Lubbock, J. W. (b), 11 Oct 
Darwin gives his opinion to Sir John Lubbock, after consultation with John Innes (perpetual curate of Down), on some difficulties that have arisen in connection with the establishment of the school for the poor at Down, specifically on trust-deeds. Trust-deeds of schools applying for public funds after 1847 include ‘management clauses’ formulated by the Privy Council Committee on Education. Religious and moral instruction remained, under the provisions of the clauses, and the responsibility fell to the minister, and the direction of the school was placed in the hands of a committee comprised of the minister, the curate, and a number of local residents who subscribed to the support of the school. Failure to comply with this requirement resulted in the loss of public monies for the school.
Letter 9122 — Darwin, C. R. to Down School Board, [Nov–Dec 1873]
Darwin, Sir John Lubbock, Ellen Frances Lubbock, and S. E. Wedgwood, petition the Board to grant permission for the school hall to be used as a reading room in the evening during winter. It was mentioned that the late Vicar appreciated the advantages of such an institution.
Letter 12879 — Darwin, C. R. to Fegan, J. W. C., [Dec 1880 – Feb 1881]
Darwin writes to J. W. C Fegan, a nonconformist evangelist saying he gladly turns the reading room over to him for his mission work. He says through Fegan’s gospel services there is not a drunkard left in the village.
Curates and Scandal
Letter 6223 — Horsman, S. J. H. to Darwin, C. R., 2 June 
Horsman attempts to convince Darwin that he only intended to be away for a short amount of time, but upon hearing rumours about himself coupled with his unhappiness in Down, he will resign curacy of Down.
Letter 6241 — Innes, J. B. to Darwin, C. R., 13 June 1868
J. B. Innes, vicar of Down writes to Darwin about difficulties in which Horsman, curate at Down, has involved himself and others. Horsman has said he would resign. Innes offers to give up his interests in the living at Down.
Letter 6486 — Darwin, C. R. to Innes, J. B., 1 Dec 1868
Darwin writes to J. B. Innes, vicar of Down about the problems with the next curate, Mr Robinson, who has suddenly departed for Ireland for a month. Darwin says the parish urgently needs some respectable man to hold the living permanently.
Letter 6492 — Innes, J. B. to Darwin, C. R., 4 Dec 1868
J. B. Innes, vicar of Down provides Darwin with the full background on the difficulties of the vicarage of Down.
Letter 6501 — Innes, J. B. to Darwin, C. R., 12 Dec 1868
J. B. Innes, vicar of Down is concerned about the rumours regarding John Robinson [curate of Down]. He will seek to get the facts and will try to protect Robinson against malicious rumours, but if he is immoral he must go forthwith.