=Statement of Explanation.=--Any habit, like any appetite or instinct, represents something formed, set; whether this has occurred in the history of the race or of the individual makes little difference to its established urgency. Habit is second, if not first, nature. (1) Habit represents _facilities_; what is set, organized, is relatively easy. It _marks the line of least resistance_. A habit of reflection, so far as it is a specialized habit, is as easy and natural to follow as an organic appetite. (2) Moreover, the exercise of any easy, frictionless habit is pleasurable. It is a commonplace that use and wont deprive situations of originally disagreeable features. (3) Finally, a formed habit is an active _tendency_. It only needs an appropriate stimulus to set it going; frequently the mere absence of any strong obstacle serves to release its pent-up energy. It is a propensity to act in a certain way whenever opportunity presents. Failure to function is uncomfortable and arouses feelings of irritation or lack. Reluctance to the right end, an aversion requiring to be overcome, if at all, by recognition of the superior value of the right end, is then to be accounted for _on the ground of the inertia or momentum of any organized, established tendency_. This momentum gives the common ground to instinctive impulses and deliberately formed habits. The momentum represents the _old_, an adaptation to familiar, customary conditions. So far as similar conditions recur, the formed power functions economically and effectively, supplying ease, promptness, certainty, and agreeableness to the execution of an act. But if new, changed conditions require a serious readjustment of the old habit or appetite, the natural tendency will be to resist this demand. Thus we have precisely the traits of reluctance and constraint which mark the consciousness of duty. A self without habits, one loose and fluid, in which change in one direction is just as easy as in another, would not have the sense of duty. A self with no new possibilities, rigidly set in conditions and perfectly accommodated to them, would not have it. But definite, persistent, urgent tendencies to act in a given way, occurring at the same time with other incompatible tendencies which represent the self more adequately and yet are not organized into habits, afford the conditions of the sense of restraint. If for any reason the unorganized tendency is judged to be the truer expression of self, we have also the sense of lawful constraint. _The constraint of appetite and desire is a phenomenon of practical readjustment, within the structure of character, due to conflict of tendencies so irreconcilable in their existing forms as to demand radical redirection._