activity in matter.  If the bicyclist stops, his wheel falls down; no mechanical contrivance could be devised that could take his place on the wheel, and no combination of purely chemical and physical forces can alone do with matter what life does with it.  The analogy here hinted at is only tentative.  I would not imply that the relation of life to matter is merely mechanical and external, like that of the rider to his wheel.  In life, the rider and his wheel are one, but when life vanishes, the wheel falls down.  The chemical and physical activity of matter is perpetual; with a high-power microscope we may see the Brunonian movement in liquids and gases any time and at all times, but the movement we call vitality dominates these and turns them to new ends.  I suppose the nature of the activity of the bombarding molecules of gases and liquids is the same in our bodies as out; that turmoil of the particles goes on forever; it is, in itself, blind, fateful, purposeless; but life furnishes, or is, an organizing principle that brings order and purpose out of this chaos.  It does not annul any of the mechanical or chemical principles, but under its tutelage or inspiration they produce a host of new substances, and a world of new and beautiful and wonderful forms.

IV

Bergson says the intellect is characterized by a natural inability to understand life.  Certain it is, I think, that science alone cannot grasp its mystery.  We must finally appeal to philosophy; we must have recourse to ideal values—­to a non-scientific or super-scientific principle.  We cannot live intellectually or emotionally upon science alone.  Science reveals to us the relations and inter-dependence of things in the physical world and their relations to our physical well-being; philosophy reveals their relations to our mental and spiritual life, their meanings and their ideal values.  Poor, indeed, is the man who has no philosophy, no commanding outlook over the tangles and contradictions of the world of sense.  There is probably some unknown and unknowable factor involved in the genesis of life, but that that factor or principle does not belong to the natural, universal order is unthinkable.  Yet to fail to see that what we must call intelligence pervades and is active in all organic nature is to be spiritually blind.  But to see it as something foreign to or separable from nature is to do violence to our faith in the constancy and sufficiency of the natural order.  One star differeth from another in glory.  There are degrees of mystery in the universe.  The most mystifying thing in inorganic nature is electricity,—­that disembodied energy that slumbers in the ultimate particles of matter, unseen, unfelt, unknown, till it suddenly leaps forth with such terrible vividness and power on the face of the storm, or till we summon it through the transformation of some other form of energy.  A still higher and more inscrutable mystery is life, that something which clothes itself in each infinitely varied and beautiful as well as unbeautiful form of matter.  We can evoke electricity at will from many different sources, but we can evoke life only from other life; the biogenetic law is inviolable.