In order to explain ourselves clearly as to the conception of method, and method of action, which play such an important part in War, we must be allowed to cast a hasty glance at the logical hierarchy through which, as through regularly constituted official functionaries, the world of action is governed.
Law, in the widest sense strictly applying to perception as well as action, has plainly something subjective and arbitrary in its literal meaning, and expresses just that on which we and those things external to us are dependent. As a subject of cognition, Law is the relation of things and their effects to one another; as a subject of the will, it is a motive of action, and is then equivalent to command or prohibition.
Principle is likewise such a law for action, except that it has not the formal definite meaning, but is only the spirit and sense of law in order to leave the judgment more freedom of application when the diversity of the real world cannot be laid hold of under the definite form of a law. As the judgment must of itself suggest the cases in which the principle is not applicable, the latter therefore becomes in that way a real aid or guiding star for the person acting.
Principle is objective when it is the result of objective truth, and consequently of equal value for all men; it is subjective, and then generally called maxim if there are subjective relations in it, and if it therefore has a certain value only for the person himself who makes it.
Rule is frequently taken in the sense of Law, and then means the same as Principle, for we say “no rule without exceptions,” but we do not say “no law without exceptions,” a sign that with Rule we retain to ourselves more freedom of application.