The real sting here isn't that we're all biased—we know that already. Rather, Marcus is suggesting something far lonelier: that even our most careful observations come pre-filtered through our own nature, and there's no vantage point from which to step outside ourselves and compare our perspective to "the truth" itself. A doctor and a patient hear the same diagnosis, yet one absorbs it as manageable data while the other hears a death sentence, and both are genuinely experiencing their own reality. What saves us from despair, Marcus implies, is accepting this limitation not as defeat but as the honest starting point for how we should treat others—with the humility that their different reading of the world isn't stupidity or malice, but simply the unavoidable consequence of being human.