[Carl Jung on Prophetic Dreams.]
Just as memories that have long since fallen below the threshold are still accessible to the unconscious, so also are certain very fine subliminal combinations that point forward, and these are of the greatest significance for future events in so far as the latter are conditioned by our psychology.
But no more than the science of history bothers itself with future combinations of events, which are rather the object of political science, can the forward-pointing psychological combinations be the object of analysis; they would be much more the object of a refined psychological syntheticism that knew how to follow the natural currents of libido.
This we cannot do, or only badly; but it happens easily enough in the unconscious, and it seems as if from time to time, under certain conditions, important fragments of-this-work come to light, at least in dreams, thus accounting for the prophetic significance of dreams long claimed by superstition.
Dreams are very often anticipations of future alterations of consciousness. (CW 5; fn 18)