Defense mechanism

A defense mechanism is an unconscious psychological process that protects the self from anxiety by distorting, denying, or redirecting threatening thoughts, feelings, or impulses. First catalogued by Sigmund Freud and later elaborated by his daughter Anna Freud, defense mechanisms are not deliberate strategies but automatic regulatory responses — the mind's homeostatic system maintaining the coherence of the self-model against contradictory evidence.

Freud identified repression as the foundational defense: the banishment of unacceptable material from consciousness. Later theorists added projection (attributing one's own impulses to others), denial (refusing to acknowledge external reality), sublimation (redirecting impulses into socially acceptable activities), and splitting (dividing experience into all-good and all-bad categories). From a systems perspective, each defense is a feedback loop that stabilizes the self-model by filtering input rather than updating the model.

The clinical significance of defenses lies in their rigidity. A flexible defense system adapts to circumstance; a rigid one applies the same filter regardless of context, producing the self-sealing structure that Wilfred Bion observed in both individuals and groups.