have here the
continuous force which binds age to age, which enables each to begin
with some improvement on the last, if the last did itself improve;
which makes each civilisation not a set of detached dots, but a line of
colour, surely enhancing shade by shade. There is, by this doctrine, a
physical cause of improvement from generation to generation: and no
imagination which has apprehended it can forget it; but unless you
appreciate that cause in its subtle materialism, unless you see it, as
it were, playing upon the nerves of men, and, age after age, making
nicer music from finer chords, you cannot comprehend the principle of
inheritance either in its mystery or its power.

These principles are quite independent of any theory as to the nature
of matter, or the nature of mind. They are as true upon the theory that
mind acts on matter--though separate and altogether different from
it--as upon the theory of Bishop Berkeley that there is no matter, but
only mind; or upon the contrary theory--that there is no mind, but only
matter; or upon the yet subtler theory now often held--that both mind
and matter are different modifications of some one tertium quid, some
hidden thing or force. All these theories admit--indeed they are but
various theories to account for--the fact that what we call matter has
consequences in what we call mind, and that what we call mind produces
results in what we call matter; and the doctrines I quote assume only
that. Our mind in some strange way acts on our nerves, and our nerves
in some equally strange way store up the consequences, and somehow the
result, as a rule and commonly enough, goes down to our descendants;
these primitive facts all theories admit, and all of them labour to
explain.

Nor have these plain principles any relation to the old difficulties of
necessity and freewill. Every Freewillist holds that the special force
of free volition is applied to the pre-existing forces of our corporeal
structure; he does not consider it as an agency acting in vacuo, but as
an agency acting upon other agencies. Every Freewillist holds that,
upon the whole, if you strengthen the motive in a given direction,
mankind tend more to act in that direction. Better motives--better
impulses, rather--come from a good body: worse motives or worse
impulses come from a bad body. A Freewillist may admit as much as a
Necessarian that such improved conditions tend to improve human action,
and that deteriorated