ly derived from the same source.
Rightly elucidated, the philosophical historian will find in it an
invaluable clue to the unravelment of the tangled skein of human
endeavor.

Historic periodicity is on the one side an organic law of memory,
dependent upon the revival of transmitted ancestral impressions. A
prevailing idea though over-cultivation exhausts its organic correlate,
and leads to defective nutrition of that part in the offspring. Hence
they do not pursue the same idea as their fathers, but revert to a
remoter ancestral historic idea, the organic correlate of which has
lain fallow, thus gained strength. It is brought forth as new, receives
additions by contiguity and similarity, is ardently pursued,
over-cultivated, and in time supplanted by another revival.

But this material side corresponds to an all-important mental one. As an
organic process only, the history of periodic ideas is thus
satisfactorily explained, but he who holds this explanation to be
exhaustive sees but half the problem.

The permanence of a historic idea, I have stated, is in direct
proportion to the number of true ideas in its composition; the
impression it makes on the organic substrata of memory is in turn in
proportion to its permanence. The element of decay is the destructive
effects of natural trains of thought out of accord with the logically
true trains. These cause defective cerebral nutrition, which is thus
seen to arise, so far as influenced by the operations of the memory,
from relations of truth and error. There is a physiological tendency in
the former to preserve and maintain in activity; in the latter to
disappear. The percentage of true concepts which makes up the complexity
of a historic idea gives the principal factor towards calculating its
probable recurrence. Of course, a second factor is the physiological one
of nutrition itself.

The next important distinction in discussing historic ideas is between
those which are held consciously, and those which operate
unconsciously. The former are always found to be more active, and more
amenable to correction. An unconscious idea is a product of the natural,
not the logical laws of mind, and is therefore very apt to be largely
false. It is always displaced with advantage by a conscious aim.

One of the superficial fallacies of the day, which pass under the name
of philosophy, is to maintain that any such historic idea is the best
possible one for the time and place in w