mental thing--is solid and unchanging. But this is an illusion. The
seemingly unchanging features are changeless only in the monotony of
their constant mutation.

Cohering masses are rigid in respect only of the constancy of the
dynamic process of transmutation in which cohesion consists. The sun
shines eternally steady only in consequence of the ceaseless kinetic
energies which give it being.

What we are ever doing in rational Discourse, what Knowledge constantly
accomplishes, is to furnish an account, a reproduction of a series of
operations. The World is a process--an activity. That was recognised as
long ago as the days of Heracleitus, but his disciples did
not--although we think there is good ground for believing that he
did[60:1]--his disciples did not realise that a process, whilst it
implies constant flux and change, implies also something permanent even
in its mutations, something which undergoes the change and sustains the
flow.

To understand a thing is to discover how it _operates_. The eternal
forms of things are laws of natural action. Such are the law of
gravitation, the laws of optics or of chemical combination. A static
picture unless so interpreted must be at once valueless and meaningless.

It follows that Thought and Discourse, in furnishing us with Knowledge,
must themselves be active, and must in some way or other reproduce the
activity of Nature. Thought, in short, _is_ an Activity which reproduces
the activity of things, the activity in which the phenomena of Nature
arise.

But how do we arrive at any apprehension of Natural Action? What informs
us that Nature is a potency ever operative? What suggests to us the
conception of potency at all? We reply that we arrive at the idea of
potent action because we are ourselves active beings. Our organism
maintains itself by constant physiological activities. These are the
permanent constancies of transmutation which _constitute_ the organism.

But superimposed upon these there are our voluntary exertional
activities. By these latter we necessarily mingle with and indeed
participate in the action of the natural forces which (as we usually
say) surround us, but which in point of fact do more than surround us.
The disparate grouping of natural bodies in vision blinds us to the fact
that we are really not merely surrounded by but are mingled with and
participate in the dynamic system.[61:1] We are continually pressing
with our weight upon the bodies o