Our space is called three-dimensional because it takes three
numbers--measurement in three mutually perpendicular directions--to
determine and mark out any particular point from the totality of
points. Time, as the individual experiences it, is called
one-dimensional for an analogous reason: one number is all that is
required to determine and mark out any particular event of a series
from all the rest. Now in order to establish a position in a space of
four dimensions it would be necessary to measure in _four_ mutually
perpendicular directions. Time curvature opens up the possibility of
a corresponding higher development in time: one whereby time would
be more fittingly symbolized by a plane than by a linear figure.
Indeed, the familiar mystery of memory calls for such a conception.
Memory is a carrying forward of the past into the present, and the
fact that we can recall a past event without mentally rehearsing
all the intermediate happenings in inverse order, shows that in
the time aspect of memory there is simultaneity as well as
sequence--time ceases to be linear and becomes _plane_. More
remarkable illustrations of the sublimation of the time-sense are
to be found in the phenomena of sleep and dreams.
"Oh, thou that sleepest, what is sleep?" asks the curious Leonardo.
Modern psychological science has little to offer of a positive
nature in answer to this world-old question, but it has at least
effectively disposed of the absurd theories of the materialists who
would have us believe that sleep is a mere matter of blood
circulation or of intoxication by accumulation of waste products in
the system. Sleep states are not abnormal, but part and parcel of
the life existence of the individual. When a person is asleep he has
only become unresponsive to the mass of stimuli of the external
world which constitutes his environment. As Sidis says, "When our
interest in external existence fags and fades away, we go to sleep.
When our interests in the external world cease, we draw up the
bridges, so to say, interrupt all external communication as far as
possible, and become isolated in our own fortress and repair to our
own world of organic activity and inner dream life. Sleep is the
interruption of our intercourse with the external world: it is the
laying down of our arms in the struggle of life. Sleep is a truce
with the world."
The twin concepts of higher space and curved time sanction a view of
sleep even bolder. Sleep is more than a longing of the body to be
free of the flame which consumes it: the flame itself aspires to be
free--that is to say, consciousness, tiring of its tool, the brain,
and of the world, its workshop, takes a turn into the plaisance of
the fourth dimension, where time and space are less rigid to resist
the fulfillment of desire.