"Truth, Justice, and the American Way" has long been Superman's motto, another inheritance from his ventures outside comics and into other media.
Like many superthings, this motto has to some degree been generalized to the DCU as a whole. In that context, the common view is that the pillars of the DCU, the "Big Three", the Superheroic Trinity, each hew most to one of the three principles. Wonder Woman represents "Truth", Batman "Justice", and Superman "the American Way".
But I don't see it that way at all.
I suppose people associate Wonder Woman with the idea of "Truth", because of her magic lasso. But I always remember that the lasso was not part of Wonder Woman's armament; Marston added it later, and it gave Diana control over the person ensnared, not merely the ability to force the truth from them. It was just another of Marston's "dominatrix" props. Sigh.
I've read as many WW stories as most people have, and my impression is that they seldom involved any sort of "search for the truth" (except, perhaps, where the enemy is hiding). I'd be hard pressed, using evidence from her adventures, to depict her role as "Seeker of Truth". She is, at heart, your standard monster-bashing classical adventurer, not an Oedipus-the-detective or Oedipus-the-suffering-sage.
Wonder Woman, as her Countdown storyline showed, is about "Justice" and by that I mean, not the "show them the system works" justice of a Commissioner Gordon but the "I'll just tie you to this here anthill and walk away" justice of a Jonah Hex. Not due process; not trial by jury. Old-fashioned neck-snapping Justice.
To me, it's Superman who's about the Truth. Does that seem off, given that a huge chunk of super-storytime has focused on efforts to keep his civilian identity secret, even from his closest friends? Perhaps. But Superman's story (as Johns and Busiek are recently reminding us) is really Clark Kent's story. Clark Kent is Superman's "truth" he must protect. Clark Kent, the crusading reporter, whose job is to unearth truths and expose them for the world to see. Clark Kent's life is devoted to pursuing, and sharing, the truth.
C'mon! A wealthy industrialist who embodies the American ethos of social Darwinism? Who still chooses to use his power for the benefit of society? Who, through his indomitable spirit, turns his own personal tragedy into a public good? Who believes in family, redemption, and public service?
Citizens, Batman is the American Way.