The essential difference consists in this, that war is no activity of the will, which exerts itself upon inanimate matter like the mechanical arts; or upon a living but still passive and yielding subject, like the human mind and the human feelings in the ideal arts, but against a living and reacting force. How little the categories of arts and sciences are applicable to such an activity strikes us at once; and we can understand at the same time how that constant seeking and striving after laws like those which may be developed out of the dead material world could not but lead to constant errors. And yet it is just the mechanical arts that some people would imitate in the art of war. The imitation of the ideal arts was quite out of the question, because these themselves dispense too much with laws and rules, and those hitherto tried, always acknowledged as insufficient and one-sided, are perpetually undermined and washed away by the current of opinions, feelings, and customs.

Whether such a conflict of the living, as takes place and is settled in war, is subject to general laws, and whether these are capable of indicating a useful line of action, will be partly investigated in this book; but so much is evident in itself, that this, like every other subject which does not surpass our powers of understanding, may be lighted up, and be made more or less plain in its inner relations by an inquiring mind, and that alone is sufficient to realise the idea of a theory.