St. Francis . . . writes . . . "the sun is our second heart." Connecting ancient spiritual insight with evolutionary biology, Thich Nhat Hanh has concluded that:
In our former lives, we were rocks, clouds and trees. We may have been an oak tree ourselves. This is not just Buddhist; it is scientific. We humans are a very young species. We appeared on earth only recently. We were plants, we were trees, and now we have become humans. We have to remember our past existences and be humble. We can learn the Dharma from an oak tree.
— Tom Hayden, Thich Nhat Hanh, St. Francis , , The Lost Gospel of the Earth by Tom Hayden