"Not mere abstract talk"

When we reach the subject of mysticism, you will undergo so deep an immersion into these exalted states of consciousness as to be wet all over, if I may so express myself; and the cold shiver of doubt with which this little sprinkling may affect you will have long since passed away doubt, I mean, as to whether all such writing be not mere abstract talk and rhetoric set down pour encourager les autres. You will then be convinced, I trust, that these states of consciousness of "union" form a perfectly definite class of experiences, of which the soul may occasionally partake, and which certain persons may live by in a deeper sense than they live by anything else with which they have acquaintance.

-- William James, The Varieties of Religious Experience, Lecture 5

You can listen to this lecture and others by William James by going here (links to YouTube).