In Mysticism and Philosophy (1960) W. T. Stace distinguished extrovertive mystical experience, in which the many things of the world are seen as one, from introvertive experience, in which the mind empties of all content and finds a unity without distinctions. He held the introvertive the more complete, and both alike across cultures.
Extrovertive and Introvertive Mysticism
W. T. Stace’s distinction between unity seen in the world and unity found in empty consciousness.
Also: Stace’s typology