These experiences also convinced me that mystical forms of Christianity are true, and that the mystical forms of all the enduring religions of the world are true.

My experiences were what scholars of mysticism call “extravertive” or “eyes open” mystical experiences (the other type is “introvertive” or “eyes closed”). I saw the same visual “landscape” – a forest, a room, the inside of an airliner – that I normally see. There were no extra beings, no angels.

For a minute or two (and once for the better part of an hour), what I was seeing looked very different. Light became different – as if there were a radiance shining through everything. The biblical phrase for this is “the glory of God” – as the book of Isaiah puts it, “the earth is filled with the glory – the radiance – of God. The world was transfigured, even as it remained “the same.” And I experienced a falling away of the subject-object distinction that marks our ordinary everyday experience – that sense of being a separate self, “in here,” while the world is “out there.”

They were experiences of wonder – not of curiosity, but of what the 20th century Jewish theologian Abraham Heschel called “radical amazement.”

They were also experiences in which I felt that I was seeing more clearly than I ever had before – that what I was experiencing was “the way things are.” And they were also experiences of complete peacefulness, marked by a sense that I would love to stay in this mental state forever. Anxiety and distraction utterly disappeared. Everything looked beautiful.

When I had these experiences, I had no intellectual understanding of mysticism. Indeed, whenever I tried to read mystical writings, they seemed like gobbledy-gook. I had no idea what they were about – they were completely opaque. But after these experiences, mystical texts became luminous. I recognized in them what I had experienced.

The effect was to transform my understanding of the word “God.” I began to understand that the word does not refer to a person-like being “out there,” beyond the universe – an understanding of “God” that ceased to be persuasive in my teens and twenties.

I began to understand that the word “God” refers to “what is” experienced as wondrous and compelling, as, to use William James’ phrase, “the more” which is all around us. Or to use a phrase from the New Testament, the word “God” refers to “the one in whom we live and move and have our being” (Acts 17.28). “God” is not a hypothesis, but a reality who can be known.

Thus, to argue about whether God exists seems to me to be based on a misunderstanding of what the word points to. If “God” means a person-like being “out there,” completely separate from the universe, then I am an atheist. I do not believe there is such a being. But if the word “God” points to a radiance that pervades “what is,” as I now think – then, of course, God is real. Not just the God of Christianity, but the God of all the enduring religions.