UPDATE: I plan a flip return to blogging, and find myself seriously thinking on a subject. Rats.
Why don't we settle disputes with force? Or rather, why do we look on it as a last resort, since we do (and have quite recently) so settle them? We are assuming that reason is more than a working out of will-to-power. In fact, we are assuming that reason can accurately represent reality in such a way as to allow us to make predictions about it. If we truly thought that reason was entirely disconnected from reality ("Whose reality? Yours or mine?"), we would assume that it could never tell us anything about the actions we should take.
Taking the strong opposite, if we assume that reality is nothing but Reason ("Granted: that all force can be explained as the workings of these [wills-to-power]...." --Nietzsche), we can view the working out of a battle or a fistfight as the flowering of Geist. Only the view that reason can come to true conclusions about the causal world, but that such a world is not, itself, Reason, allows us to avoid hitting each other. It's a view I myself hold, but, as I said above, I'm willing to make exceptions.