selection, work upon species to modify them, if there were not something
in species pushing out and on, seeking new ways, new forms, in fact some
active principle that is modifiable?

Life has risen by stepping-stones of its dead self to higher things. Why
has it risen? Why did it not keep on the same level, and go through the
cycle of change, as the inorganic does, without attaining to higher
forms? Because, it may be replied, it was life, and not mere matter and
motion--something that lifts matter and motion to a new plane.

Under the influence of the life impulse, the old routine of matter--from
compound to compound, from solid to fluid, from fluid to gaseous, from
rock to soil, the cycle always ending where it began--is broken into,
and cycles of a new order are instituted. From the stable equilibrium
which dead matter is always seeking, the same matter in the vital
circuit is always seeking the state of unstable equilibrium, or rather
is forever passing between the two, and evolving the myriad forms of
life in the passage. It is hard to think of the process as the work of
the physical and chemical forces of inorganic nature, without
supplementing them with a new and different force.

The forces of life are constructive forces, and they are operative in a
world of destructive or disintegrating forces which oppose them and
which they overcome. The physical and chemical forces of dead matter are
at war with the forces of life, till life overcomes and uses them.

The mechanical forces go on repeating or dividing through the same
cycles forever and ever, seeking a stable condition, but the vital force
is inventive and creative and constantly breaks the repose that organic
nature seeks to impose upon it.