Hi Shaista! I think the first paragraph really lays out what the author is discussing, and that is the complexity of Darwin's beliefs. The author then talks about Darwin as Christian, Atheist, or Agnostic, then ends with the idea that Darwin is not an Atheist, as most people would assume. I think the Main Idea would have to speak to this - that Darwin's beliefs about religion versus science are complex. A minor idea that supports this, is that one does not have to be Atheist to embrace Darwin's ideas, as the Victorians were considered to be very religious, but still believed that Darwin's theories were possible.