I read his book "The Grand Design". He says there is no God to create this universe - according to his M-theory. Anyway, I think he has nothing to deny Spiritual World. As he said, M-theory postulated the big bang is possible to create 10^500 types of universe, he believes there are multi-universes. The so-called spiritual world could be one of the multi-universes, of different dimensions. Therefore, gods and ghosts could be one type of living existence living in different dimensions. After all, Stephen Hawking can not provide any evidence to deny spirituality.