To be sure, any normative system, especially the legal system, understands the bottom line in terms of action — that’s just the nature of law. But if our interest is in reason, as with reasonable doubt, then it is interested in justification as a means to arriving at correct action; and there is no evidentiary justification, nor can there be, without the subgoal of pursuing something that gives us a sense of closure by means of the highest conceivable standards (which we quaintly dub “truth”). If it were otherwise, the words “justification”, “correct”, and “reason” would be entirely without meaning, and we’d be unable to distinguish the justified from the unjustified, the correct from the incorrect, etc.; since they only have meaning relative to some standard(s) or other (though those standards, in turn, arise from intuitions cemented as prototypes).

Discovery of truth might not always achieve the main goal (correct action), and moreover, arguably we can never really know the whole truth about anything (our standards may always be lacking). But that doesn’t excuse the legal system in suddenly deciding to give it up entirely. To do so would be to tacitly give up evidentiary justification, and thus would be an exercize in giving leave to arbitrary action and judgment (either directly, or through the bad habits that it creates). The abandon of non-arbitrariness leads to lack of regard for the rule of law. And so, in a single fell swoop, with the removal of truth as a subgoal, we make justification impossible, make judgments arbitrary, and destroy the rule of law. That consequence is diametrically opposed to the functions of Western legal systems.

And that’s just the matter of epistemology. In some sense, the epistemic trouble has an excuse for being complicated, and gives us a dim sense of why the legal system is supposed to be legitimate: to hear these troubling arguments and make the evidence fit our laws. But if the question is semantic, not epistemic, then it is difficult for me to see what excuse we have for uncertainty.