An atheist cannot be spiritual. But you must understand that even a theist cannot be spiritual. Because an atheist and a theist are not different. One believes there is God, another believes there is no God. Both of them are believing something that they do not know. You are not sincere enough to admit that you do not know, that’s your problem. So theists and atheists are not different. They are the same people putting up an act of being different. A spiritual seeker is neither a theist nor an atheist. He has realized that he does not know, so he is seeking.
The moment you believe something, you become blind to everything else. The whole conflict on the planet is not between good and evil as they are trying to project it. It is always one man’s belief versus another man’s belief. The need for belief is more psychological than spiritual. You want to cling to something, you want to feel secure, and you want to feel like you know it all. That is coming from a very immature mind. What is the problem if you don’t know anything about this existence? You actually don’t know anything. It’s beautiful! And you see how to make yourself beautiful and joyful within yourself, which is within your hands.