THE DIFFICULTY OF THEORY AS SOON AS MORAL QUANTITIES COME INTO CONSIDERATION.
Every theory becomes infinitely more difficult from the moment that it touches on the province of moral quantities.

Architecture and painting know quite well what they are about as long as they have only to do with matter; there is no dispute about mechanical or optical construction.
But as soon as the moral activities begin their work, as soon as moral impressions and feelings are produced, the whole set of rules dissolves into vague ideas.
The science of medicine is chiefly engaged with bodily phenomena only; its business is with the animal organism, which, liable to perpetual change, is never exactly the same for two moments.

This makes its practice very difficult, and places the judgment of the physician above his science; but how much more difficult is the case if a moral effect is added, and how much higher must we place the physician of the mind?
15.

THE MORAL QUANTITIES MUST NOT BE EXCLUDED IN WAR.
But now the activity in War is never directed solely against matter; it is always at the same time directed against the intelligent force which gives life to this matter, and to separate the two from each other is impossible.
But the intelligent forces are only visible to the inner eye, and this is different in each person, and often different in the same person at different times.
As danger is the general element in which everything moves in War, it is also chiefly by courage, the feeling of one's own power, that the judgment is differently influenced.

It is to a certain extent the crystalline lens through which all appearances pass before reaching the understanding.
And yet we cannot doubt that these things acquire a certain objective value simply through experience.
Every one knows the moral effect of a surprise, of an attack in flank or rear.