All depth psychology has already been summed up by this fragment of Heraclitus: “You could not discover the limits of the soul (psyche), even if you traveled every road to do so; such is the depth (bathun) of its meaning (logos).”
Ever since Heraclitus brought soul and depth together in one formulation, the dimension of soul is depth (not breadth or height) and the dimension of our soul travel is downward.
— Re-Visioning Psychology, Introduction