tive, are knocking out the
barriers of time. This fact is the vital and dynamic difference between
animal life and human life. As plants gather in and store up solar energy
into sheaves for the use and growth of animal and man--so humans are
gathering and binding the knowledge of past centuries into sheaves for the
use and development of generations yet unborn.

We have seen that the term wealth, rightly understood, means the fruit of
the time-binding work of humanity. Wealth is of two kinds: one is
material; the other is knowledge. Both kinds have use-value. The first
kind perishes--the commodities composing it deteriorate and become useless.
The other is permanent in character; it is imperishable; it may be lost or
forgotten but it does not wear out.

The one is limited in time; the other, unlimited in time; the former I
call POTENTIAL USE-VALUE; the latter, KINETIC USE-VALUE. Analysis will
justify the names. The energy of a body which is due to its position, is
called potential energy. The energy of a body which is due to its motion,
is called kinetic energy. Here the material use-value has value through
its position, shape and so forth; it is immobile if not used, and has not
the capacity to progress. Mental use-values are not static but permanently
dynamic; one thought, one discovery, is the impulse to others; they follow
the law of an increasing _potential_ function of time. (See app. II.) This
is why these names correspond to the two names of the two mentioned
classes of energy.

Here I must return to the current conceptions of wealth and capital,
before cited. "Wealth," we are told, "is any useful or agreeable thing
which possesses _ex_change_able value_." And we are told that "Capital is
that part of wealth which is devoted to obtaining further wealth." I have
said that such conceptions--such definitions--of wealth and capital are
childish--they belong to the period of humanity's childhood. That they are
indeed childish conceptions the reader can not fail to see if he will
reflect upon them and especially if he will compare them with the
scientific conception according to which wealth consists of those
things--whether they be material commodities or forms of knowledge and
understanding--that have been produced by the time-binding energies of
humanity, and according to which _nearly all the wealth of the world at
any given time_ is the _accumulated fruit of the toil of past
generations_--the living work of the