This problem is only solvable if we cease arbitrarily to substitute for the unknown x itself the conditions under which that force becomes apparent⁠—such as the commands of the general, the equipment employed, and so on⁠—mistaking these for the real significance of the factor, and if we recognize this unknown quantity in its entirety as being the greater or lesser desire to fight and to face danger. Only then, expressing known historic facts by equations and comparing the relative significance of this factor, can we hope to define the unknown.