Henry Corbin, in a 1948 talk about the comparative study of religion, called it a phenomenological discovery:
We are discovering that the I and the World, the modes of being of the personal subject and the regions of being which it explores, are not two things which get juxtaposed, but presences within each other, an interpresence, an indissoluble correlation, and a structure. It is within the general ensemble which can be termed the phenomenological orientation of the humanities. And there is also something analogous happening in the physical sciences.
— Corbin 1948 (1998, 23)
But this discovery can also be recovered from ancient scriptures.
As great as the infinite space beyond is the space within the lotus of the heart. Both heaven and earth are contained in that inner space, both fire and air, sun and moon, lightning and stars. Whether we know it in this world or know it not, everything is contained in that inner space.
— Chandogya Upanishad (Easwaran, in Harvey 1996, 38)
‘This world’? Which world? Can you put the works of the brain back in the lotus of the heart?