<*For details see a paper on "The Physiology of Laughter," publishedin Macmillan's Magazine for March, 1860, and reprinted in Essays, vol. II.>
Probably it will be thought impossible to extend this reasoning so asto include voluntary acts. Yet we are not without evidence that the transitionfrom special desires to special muscular motions, conforms to the same principle.
The mental antecedents of a voluntary movement, are such as temporarily makethe line through which this movement is initiated, the line of least resistance.
For a volition, suggested as it is by some previous thought joined with itby associations that determine the transition, is itself a representationof the movements which are willed, and of their sequences. But to representin consciousness certain of our own movements, is partially to arouse thesensations accompanying such movements, inclusive of those of muscular tension-- is partially to excite the appropriate motor-nerves and all the othernerves implicated. That is to say, the volition is itself an incipient dischargealong a line which previous experiences have rendered a line of least resistance.
And the passing of volition into action is simply a completion of the discharge.
One corollary must be noted; namely that the particular set of movementsby which an object of desire is reached, are usually movements implying thesmallest total of forces to be overcome. As the motion initiated by eachfeeling takes the line of least resistance, it is inferable that a groupof feelings constituting a more or less complex desire will initiate motionsalong a series of lines of least resistance; that is, the desired end willbe achieved with the smallest effort. Doubtless through want of knowledgeor want of skill or want of resolution to make immediate exertion, a manoften takes the more laborious of two courses. But it remains true that relativelyto his mental state at the time, his course is the easiest to him -- theone least resisted by the aggregate of his feelings. §80. As with individual men so is it with aggregations of men. Socialchanges take directions that are due to the joint actions of citizens, determinedas are those of all other changes wrought by composition of forces.
Thus when we note the direction of a nation's growth, we find it to bethat in which the aggregate of opposing forces is least. Its units have energiesto be expended in self-maintenance and reproduction. These energies are metby various antagonistic energies -- those of geologic origin, those of climate,of wild animals, of other human races with whom there is enmity or competition.
And the tracts the society spreads over, are those in which there is thesmallest total of antagonisms while they yield the best supply of food andother materials which further the genesis of energies. For these reasonsit happens that fertile valleys where water and vegetal products abound,are early peopled. Sea-shores, too, supplying much easily-gathered food,are lines along which mankind have commonly spread. The general fact that,so far as we can judge from the traces left by them, large societies firstappeared in those warm regions where the fruits of the earth are obtainablewith comparatively little exertion, and where the cost of maintaining bodilyheat is but slight, is a fact of like meaning. And to these instances maybe added the allied one daily furnished by emigration, which we see goingon towards countries presenting the fewest obstacles to the self-preservationof individuals, and therefore to national growth. Similarly with that resistanceto the movements of a society which neighbouring societies offer. Each ofthe tribes or nations inhabiting any region, increases in numbers until itoutgrows its means of subsistence. In each there is thus a force ever pressingoutwards on to adjacent areas -- a force antagonized by like forces in thetribes or nations occupying those areas. And the wars that result -- theconquests of weaker tribes or nations, and the overrunning of their territoriesby the victors, are instances of social movements taking place in the directionsof least resistance. Nor do the conquered peoples, when they escape exterminationor enslavement, fail to show us movements which are similarly determined.
For, migrating as they do to less fertile regions -- taking refuge in desertsor among mountains -- moving in directions where the resistances to socialgrowth are comparatively great; they still do this only under an excess ofpressure in all other directions: the physical obstacles to self-preservationthey encounter; being really less than the obstacles offered by the enemiesfrom whom they fly.
