he eventually described himself as (more or less) agnostic.
We know that Darwin had not a shred of doubt about the power of natural selection to modify and transmute species. The questions were in the details of how it operated. Darwin’s correspondence shows that his religious beliefs changed substantially over the course of this life, and that they never reached a fixed position. His agnosticism should be understood as a state of genuine uncertainty regarding the existence and nature of God. Darwin’s unwillingness to pronounce on religious matters stemmed from his strongly held view that science and religion rest on different foundations and forms of evidence, and that his scientific expertise, no matter how extensive, did not make him a religious authority. Running right through his early discussions on religion and science with Emma, to his publications on evolution, and later correspondence with clergymen and enquiring readers, is an agreed commitment to the practice of conscientious doubt and critical inquiry in both science and religion.
https://www.darwinproject.ac.uk/commentary/religion/what-did-darwin-believe
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