The Sublime, the Human, and the Divine in the Depth-Theology of Abraham Joshua Heschel
"Throughout his life Abraham Heschel grappled with the basic questions of religious faith. This task he called 'depth-theology' – 'to explore the depth of faith, the substratum out of which belief arises.' Heschel called this depth-theology to distinguish it from what is often meant by theology. Theology deals with the content of belief; depth-theology with the act of believing as well as with the acts that precede and nurture faith."
Merkle, John C. “The Sublime, the Human, and the Divine in the Depth-Theology of Abraham Joshua Heschel.” The Journal of Religion 58, no. 4 (1978): 365-379. http://www.jstor.org/stable/1201471