The second peculiarity in War is the living reaction, and the reciprocal action resulting therefrom. We do not here speak of the difficulty of estimating that reaction, for that is included in the difficulty before mentioned, of treating the moral powers as quantities; but of this, that reciprocal action, by its nature, opposes anything like a regular plan. The effect which any measure produces upon the enemy is the most distinct of all the data which action affords; but every theory must keep to classes (or groups) of phenomena, and can never take up the really individual case in itself: that must everywhere be left to judgment and talent. It is therefore natural that in a business such as War, which in its plan—built upon general circumstances—is so often thwarted by unexpected and singular accidents, more must generally be left to talent; and less use can be made of a _theoretical guide_ than in any other. 24. THIRD PECULIARITY.—UNCERTAINTY OF ALL DATA. Lastly, the great uncertainty of all data in War is a peculiar difficulty, because all action must, to a certain extent, be planned in a mere twilight, which in addition not unfrequently—like the effect of a fog or moonshine—gives to things exaggerated dimensions and an unnatural appearance. What this feeble light leaves indistinct to the sight talent must discover, or must be left to chance. It is therefore again talent, or the favour of fortune, on which reliance must be placed, for want of objective knowledge. 25. POSITIVE THEORY IS IMPOSSIBLE. With materials of this kind we can only say to ourselves that it is a sheer impossibility to construct for the Art of War a theory which, like a scaffolding, shall ensure to the chief actor an external support on all sides. In all those cases in which he is thrown upon his talent he would find himself away from this scaffolding of theory and in opposition to it, and, however many-sided it might be framed, the same result would ensue of which we spoke when we said that talent and genius act beyond the law, and theory is in opposition to reality. 26. MEANS LEFT BY WHICH A THEORY IS POSSIBLE (THE DIFFICULTIES ARE NOT EVERYWHERE EQUALLY GREAT). Two means present themselves of getting out of this difficulty. In the first place, what we have said of the nature of military action in general does not apply in the same manner to the action of every one, whatever may be his standing. In the lower ranks the spirit of self-sacrifice is called more into request, but the difficulties which the understanding and judgment meet with are infinitely less. The field of occurrences is more confined. Ends and means are fewer in number. Data more distinct; mostly also contained in the actually visible. But the higher we ascend the more the difficulties increase, until in the Commander-in-Chief they reach their climax, so that with him almost everything must be left to genius.