According to theosophical teaching, the power of sight peculiar
to the etheric double, a subtle counterpart of the physical
body. Etheric vision is of considerably greater power than
physical vision, and by its aid many of the phenomena of the
physical world may be examined, as well as many creatures of
a nonhuman nature that are ordinarily just outside the range
of physical vision. It responds readily to stimuli of various kinds
and becomes active under their influence.
Powell, A. E. The Etheric Double. 1926. Reprint, Wheaton, Ill.
Theosophical Publishing House, 1969.