"I learned one more thing as I read about mystical experiences; namely, people who had them most often spoke of them as experiences of God, the sacred, the Mystery with a capital M that is beyond all words. It had never occurred to me that what we call 'God' could be experienced. For me, the word had referred to a being who might or might not exist, in whom one could believe or disbelieve, or about whom one could remain uncertain. But I realized there is a cloud of witnesses, Christian and non-Christian, for whom God, the sacred, is real, an element of experience, not a hypothetical being who may or may not exist and whom we can only believe in.
"For the first time in my life, I understood the affirmation that the earth is full of 'the glory of God.' Perhaps the most familiar biblical example is in the prophet Isaiah. As he has a mystical experience of God, he hears the words, 'Holy, holy, holy is the Lord of hosts; / the whole earth is full of his glory' (6:3). It is also familiar to Christians in liturgical churches in the Sanctus: 'Holy, holy, holy Lord, God of power and might; heaven and earth are full of your glory.' 'Glory' in the Bible most often means radiance, luminosity. To affirm that heaven and earth (all that is) are full of God's glory means that everything is filled with the radiant luminosity of God. God, the sacred, pervades all that is, even though we do not often see it."