We kill because we are afraid of our own shadow, afraid that if we used a little common sense we'd have to admit that our glorious principles were wrong.

The line frames violence as a psychological defense mechanism: people “kill” not from strength or moral certainty but from fear—of ambiguity, of vulnerability, and of confronting their own contradictions. The “shadow” suggests the disowned parts of the self (cowardice, doubt, complicity) that are easier to project onto an enemy than to acknowledge internally. Miller’s jab at “glorious principles” targets ideological self-congratulation: lofty slogans can mask insecurity and rationalize brutality. The quote implies that ordinary “common sense” and honest self-scrutiny would expose how often proclaimed ideals are inconsistent with humane conduct, so fear drives people to double down on violence rather than revise their beliefs.