Here is a quotation I found in a beautiful essay, "Astronomy Lessons," by Anne Cushman, which appeared in the May 2008 edition of Shambhala Sun. There are so very many levels of meaning to be found in these few lines…
Within light there is darkness,
but do not try to understand that darkness.
Within darkness there is light,
but do not look for that light.
— Zen Chant, "Identity of Relative and Absolute"