Pars Pro Toto Thinking and Borderline Personality Disorder

Robert and Megan are newlyweds. One night, Megan tells Robert how lucky she is to have met him, how he is everything she ever wanted, her "knight in shining armor." The next day, Robert arrives home from work ten minutes later than usual, and he has forgotten to pick up the gallon of milk Megan asked him to stop for on the way home. Immediately, Megan explodes with rage. "Where were you? I bet you were sleeping with your ex! I knew it! You don't care about me. You forget everything I ask. I should have never married you."

Pars pro toto is Latin for "a part (taken) for the whole." In human psychology, pars pro toto representations characterize a defense mechanism called splitting. At different points in time, the self or the other person is seen as “all good” or “all bad,” but rarely, if ever, as being comprised—as all human beings are—of both good and bad qualities. The good or bad parts stand for the whole; they are not integrated, and the patient oscillates chaotically between these two extremes.

In the example above, Megan engages........

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