I'm an atheist and I don't know my T's belief system. I have discussed my atheism as it relates to my religious family and upbringing, and as it relates to a string of deaths in my life. (Religious people say some weird, distressing things to you when your parent dies. I think it's supposed to be comforting? But I was freaked out.) My T has been respectful of my (lack of) beliefs, which makes me feel like I don't really care what her beliefs are because we are both considering my point of view in session.