When we do anything, we are conscious of a _feeling of strength;_ we often have this sensation before the act--that is to say, while imagining the thing to do (as, for instance, at the sight of an enemy, of an obstacle, which we feel _equal to_): it is always an accompanying sensation. Instinctively we think that this feeling of strength is the cause of the action, that it is the "motive force." Our belief in causation is the belief in force and its effect; it is a transcript of our experience: in which we identify force and the feeling of force.--Force, however, never moves things; the strength which is conscious "does not set the muscles moving." "Of such a process we have no experience, no idea." "We experience as little concerning force as a motive power, as concerning the _necessity_ of a movement." Force is said to be the constraining element! "All we know is that one thing follows another;--we know nothing of either compulsion or arbitrariness in regard to the one following the other. Causality is first invented by thinking compulsion into the sequence of processes. A certain "understanding" of the thing is the result--that is to say, we humanise the process a little, we make it more "familiar"; the familiar is the known habitual fact of _human compulsion associated with the feeling of force._ 665. I have the intention of extending my arm; taking it for granted that I know as little of the physiology of the human body and of the mechanical laws of its movements as the man in the street, what could there be more vague, more bloodless, more uncertain than this intention compared with what follows it? And supposing I were the astutest of mechanics, and especially conversant with the formulæ which are applicable in this case, I should not be able to extend my arm one whit the better. Our "knowledge" and our "action" in this case lie coldly apart: as though in two different regions.--Again: Napoleon carries out a plan of campaign--what does that mean? In this case, everything concerning the consummation of the campaign is _known,_ because everything must be done through words of command: but even here subordinates are taken for granted, who apply and adapt the general plan to the particular emergency, to the degree of strength, etc. 666.