The Macbeth Effect, named for Lady Macbeth who tries to wash away her guilt through hand washing, is the psychological tendency to link physical cleansing with moral cleansing. What we see in Lady Macbeth is another form of magical thinking, the belief that physical washing has a causal effect in moral purification. The link here between physical and spiritual washing isn’t simply symbolic (i.e., the physical washing symbolizes the spiritual transformation) but causal (i.e., the physical washing effects the spiritual cleansing).
