Why don't we talk about Van Gogh's Christian faith?

Vincent Van Gogh has been airbrushed by the secular arts media. I have not yet seen the new exhibition at Tate Britain about his London years, so I can only comment on the publicity I have read and heard. This arts chatter downplays, or even ignores, the central feature of his life at this time: his religious zeal. It gives the impression that he was dedicating himself to art, gearing up to be the archetypal creative genius. In reality he did not take art fully seriously in the mid 1870s: though he worked for an art dealer, his real passion was religion. This is not mentioned in the articles about the show I have seen, nor was it mentioned on a radio discussion I heard: instead we hear about his immersion in Dickens and George Eliot, and the possible influence of certain English painters on his later work.