This power, as we saw, rests on a material basis, but finds expression in ethical values.

War therefore seems imperative when, although the material basis of power is not threatened, the moral influence of the State (and this is the ultimate point at issue) seems to be prejudiced.

Thus apparently trifling causes may under certain circumstances constitute a fully justifiable _casus belli_ if the honour of the State, and consequently its moral prestige, are endangered.

This prestige is an essential part of its power.

An antagonist must never be allowed to believe that there is any lack of determination to assert this prestige, even if the sword must be drawn to do so.
In deciding for war or peace, the next important consideration is whether the question under discussion is sufficiently vital for the power of the State to justify the determination to fight; whether the inevitable dangers and miseries of a war do not threaten to inflict greater injury on the interests of the State than the disadvantages which, according to human calculation, must result if war is not declared.