Let us consider again the horse-car conductor (see Sec. LVI). After he has analyzed the situation which faces him and decided that a given course of conduct is the one which fits the situation, does he require some additional faculty to inform him that this course is the one which should be followed? The analysis of practical ideas, that is, of proposed ends of conduct, is from the first an analysis of what should be done. Such being the case, it is no marvel that the conclusion of the reflection is: "This should (ought to) be done."
Indeed, just as every judgment about existent fact naturally takes the form 'S _is_ P', so every judgment regarding an activity which executes an idea takes the form, 'S ought (or ought not) to be P'. It requires no additional faculty of mind, after intelligence has been studying the motions of the moon, to insert itself, and affirm some objective relation or truth--as that the moon's motions are explainable by the law of gravitation. It is the very essence of theoretical judgment, judgment regarding fact, to state truth--what is. And it is the very essence of practical judgment, judgment regarding deeds, to state that active relation which we call obligation, what _ought to be_.
The judgment as to what a practical situation _is_, is an untrue or abstract judgment.
The practical situation is itself an _activity_; the needs, powers, and circumstances which make it are moving on. At no instant in time is the scene quiescent. But the agent, in order to determine his course of action in view of this situation, has to _fix_ it; he has to arrest its onward movement in order to tell what it is. So his abstracting intellect cuts a cross-section through its on-going, and says 'This _is_ the situation'. Now the judgment 'This ought to be the situation', or 'in view of the situation, my conduct ought to be thus and so', is simply restoring the movement which the mind has temporarily put out of sight. By means of its cross-section, intelligence has detected the principle, or law of movement, of the situation, and it is on the basis of this movement that conscience declares what ought to be.
Just as the fact of moral law, or of authority, of the incumbency of duty, needs for its explanation no separation of the 'is' from the 'ought' (see LVI), but only recognition of the law of the 'is' which is, perforce, a law of movement, and of change;--so the consciousness of law, 'the sense of obligation' requires no special mental faculty which may declare what ought to be. The intelligence that is capable of declaring truth, or what is, is capable also of making known obligation. For obligation is only _practical_ truth, the 'is' of doing.