Mysticism, according to its historical and psychological definitions, is the direct intuition or experience of God; and a mystic is a person who has, to a greater or less degree, such a direct experience -- one whose religion and life are centered, not merely on an accepted belief or practice, but on that which the person regards as first hand personal knowledge.
Evelyn UnderhillIdealism, though just in its premises, and often daring and honest in their application, is stultified by the exclusive intellectualism of its own methods: by its fatal trust in the squirrel-work of the industrious brain instead of the piercing vision of the desirous heart. It interests man, but does not involve him in its processes: does not catch him up to the new and more real life which it describes. Hence the thing that matters, the living thing, has somehow escaped it; and its observations bear the same relation to reality as the art of the anatomist does to the mystery of birth.
Evelyn Underhill