Let's say you're the passenger in a car that is approaching a set of railroad tracks. You see and hear a train approaching at great speed, and worry because your friend, the driver, doesn't seem to realize it. You tell him about the train, but he says, "Naw, there's hardly ever a train at this crossing." "Well, there is now, and we're about to be hit by it!" you say. "Naw, I'm not believing it" says your Postmodern friend, as the locomotive races closer and the conductor lays on the warning whistle.
Seems unrealistic, doesn't it? Of course it is. And it highlights the fact that we all know--though Postmodernists like to kid themselves into thinking differently--that the truth value of the statement
There is a train approaching from the left!depends not upon the observers but upon the train. When life is on the line, no one can afford to take a subjectivist view of truth, and no one does. We live our lives according to the correspondence view of truth, because we wouldn't live long if we didn't.