because, all concentrated though I am upon the idea of the
movement, I nevertheless also realize the total conditions of the
experiment, and in the back of my mind, so to speak, or in its fringe
and margin, have the simultaneous idea that the movement is not to take
place. The mere presence of that marginal intention, without effort,
urgency, or emphasis, or any special reinforcement from my attention,
suffices to the inhibitive effect.

And this is why so few of the ideas that flit through our minds do, in
point of fact, produce their motor consequences. Life would be a curse
and a care for us if every fleeting fancy were to do so. Abstractly, the
law of ideo-motor action is true; but in the concrete our fields of
consciousness are always so complex that the inhibiting margin keeps the
centre inoperative most of the time. In all this, you see, I speak as if
ideas by their mere presence or absence determined behavior, and as if
between the ideas themselves on the one hand and the conduct on the
other there were no room for any third intermediate principle of
activity, like that called 'the will.'

If you are struck by the materialistic or fatalistic doctrines which
seem to follow this conception, I beg you to suspend your judgment for a
moment, as I shall soon have something more to say about the matter.
But, meanwhile yielding one's self to the mechanical conception of the
psychophysical organism, nothing is easier than to indulge in a picture
of the fatalistic character of human life. Man's conduct appears as the
mere resultant of all his various impulsions and inhibitions. One
object, by its presence, makes us act: another object checks our action.
Feelings aroused and ideas suggested by objects sway us one way and
another: emotions complicate the game by their mutual inhibitive
effects, the higher abolishing the lower or perhaps being itself swept
away. The life in all this becomes prudential and moral; but the
psychologic agents in the drama may be described, you see, as nothing
but the 'ideas' themselves,--ideas for the whole system of which what we
call the 'soul' or character' or 'will' of the person is nothing but a
collective name. As Hume said, the ideas are themselves the actors, the
stage, the theatre, the spectators, and the play. This is the so-called
'associationist' psychology, brought down to its radical expression: it
is useless to ignore its power as a conception. Like all conceptions,
when they bec