If we must do so, if we must grant that war originates and takes its form not from a final adjustment of the innumerable relations with which it is connected, but from some amongst them which happen to predominate; then it follows, as a matter of course, that it rests upon a play of possibilities, probabilities, good fortune and bad, in which rigorous logical deduction often gets lost, and in which it is in general a useless, inconvenient instrument for the head; then it also follows that war may be a thing which is sometimes war in a greater, sometimes in a lesser degree.
All this, theory must admit, but it is its duty to give the foremost place to the absolute form of war, and to use that form as a general point of direction, that whoever wishes to learn something from theory, may accustom himself never to lose sight of it, to regard it as the natural measure of all his hopes and fears, in order to approach it where he can, or where he must.
That a leading idea, which lies at the root of our thoughts and actions, gives them a certain tone and character, even when the immediately determining grounds come from totally different regions, is just as certain as that the painter can give this or that tone to his picture by the colours with which he lays on his ground.
Theory is indebted to the last wars for being able to do this effectually now. Without these warning examples of the destructive force of the element set free, she might have talked herself hoarse to no purpose; no one would have believed possible what all have now lived to see realised.
Would Prussia have ventured to penetrate into France in the year 1798 with 70,000 men, if she had foreseen that the reaction in case of failure would be so strong as to overthrow the old balance of power in Europe?
Would Prussia, in 1806, have made war with 100,000 against France, if she had supposed that the first pistol shot would be a spark in the heart of the mine, which would blow it into the air?