We can help ourselves out, as Haeckel does, by calling the physical forces—­such as the magnet that attracts the iron filings, the powder that explodes, the steam that drives the locomotive, and the like—­“living inorganics,” and looking upon them as acting by “living force as much as the sensitive mimosa does when it contracts its leaves at touch.”  But living force is what we are trying to differentiate from mechanical force, and what do we gain by confounding the two?  We can only look upon a living body as a machine by forming new conceptions of a machine—­a machine utterly unmechanical, which is a contradiction of terms.

A man may expend the same kind of force in thinking that he expends in chopping his wood, but that fact does not put the two kinds of activity on the same level.  There is no question but that the food consumed is the source of the energy in both cases, but in the one the energy is muscular, and in the other it is nervous.  When we speak of mental or spiritual force, we have as distinct a conception as when we speak of physical force.  It requires physical force to produce the effect that we call mental force, though how the one can result in the other is past understanding.  The law of the correlation and conservation of energy requires that what goes into the body as physical force must come out in some form of physical force—­heat, light, electricity, and so forth.

Science cannot trace force into the mental realm and connect it with our states of consciousness.  It loses track of it so completely that men like Tyndall and Huxley and Spencer pause before it as an inscrutable mystery, while John Fiske helps himself out with the conception of the soul as quite independent of the body, standing related to it as the musician is related to his instrument.  This idea is the key to Fiske’s proof of the immortality of the soul.  Finding himself face to face with an insoluble mystery, he cuts the knot, or rather, clears the chasm, by this extra-scientific leap.  Since the soul, as we know it, is inseparably bound up with physical conditions, it seems to me that a more rational explanation of the phenomenon of mentality is the conception that the physical force and substance that we use up in a mental effort or emotional experience gives rise, through some unknown kind of molecular activity, to something which is analogous to the electric current in a live wire, and which traverses the nerves and results in our changing states of consciousness.  This is the mechanistic explanation of mind, consciousness, etc., but it is the only one, or kind of one, that lends itself to scientific interpretation.  Life, spirit, consciousness, may be a mode of motion as distinct from all other modes of motion, such as heat, light, electricity, as these are distinct from each other.

When we speak of force of mind, force of character, we of course speak in parables, since the force here alluded to is an experience of our own minds entirely and would not suffice to move the finest dust-particle in the air.