Clairvoyance, in its time aspect, whether spontaneous,
hypnotically induced, or self-induced, is susceptible of
classification as post-vision, present vision, and prevision.
Post-vision is that in which past events are not recollected merely,
but seen or experienced. It is the past become present. Present
vision is clairvoyance of things transpiring elsewhere; the present,
remote in space, but not in time. Prevision is the future in the
present. These various orders of _clear-seeing_ transcend the limits
of the actual knowledge and experience of the seer. This
classification and these definitions are important only to us, to
whom past, present, and future stand sharply differentiated in
thought and in experience; not to the clairvoyant, who, though bound
in body to our space and time, is consciously free in a world where
these discriminations vanish. Why do they vanish? This question can
best be answered by means of a homely analogy.

For a symbol of the flow of time in waking consciousness, imagine
yourself in a railway carriage which jogs along a main-travelled
line at a rate predetermined by the time-table. You approach, reach
and pass such stations as are intersected by that particular railway,
and you get a view of the landscape which every other traveler shares.
Having once left a station, you cannot go back to it, nor can you
arrive at places further along the line before the train itself
takes you there. Compare this with the freedom to do either of these
things, and any number of others, if you suddenly change from the
train to an automobile. Then, in effect, you have the freedom of a
new dimension. In the one case, you must travel along a single line
at a uniform rate; in the other, you are able to strike out in any
direction and regulate your speed at will. You can go back to a
place after the train has left it; you can go forward to some place
ahead, before the train arrives, or you can strike out into, and
traverse, new country. In short, your freedom, temporal and spatial,
will be related to that of the train-bound traveler, somewhat as is
trance consciousness to everyday waking life.

MODIFYING THE PAST

Modern psychology has demonstrated the existence of a great
undercurrent of mental and emotional life, transcending the
individual's conscious experience, in which the most complex
processes are carried on without the individual's conscious
participation. The clearest symbol by which this fact may