This chapter addresses the limitations potentially placed on the success of revolutions by “human nature” - which in psychological terms are the hard-wired characteristics that limit change in behavior. It is argued that in the long term, even behaviors that we conceptualize as hardwired at present tend to change (particularly through changes in the environment). The avowed goals of the French, Russian, Chinese, Cuban, and Iranian revolutions are examined, and it is concluded that none of these revolutions achieved their goals. Despite failure, the regimes that survive in China, Cuba, and Iran continue to use the rhetoric of revolution. Four ways in which human nature seems to doom revolutions are considered: extremists come to power; an “ends justify the means” approach is adopted and corruption results; the style of leader–follower relations persist after revolutions, with the result that one dictatorship replaces another; and revolutionaries typically fail to set up the necessary conditions to achieve the behavioral changes necessary to reach their revolutionary goals (such as collectivization).