Although religion and psychology are generally conceived of as distinct domains, the theoretical underpinnings of certain psychological theories are inextricably related to religious ideology. This relationship is perhaps best exemplified by the theoretical and applied similarity between Buddhist principles and Albert Ellis's Rational Emotive Behaviour Therapy (REBT). Sharing a common purpose, both the Buddha and Ellis set out to improve the human condition, and to do so in a rational, empirical manner. The significance of these parallels is discussed in relation to the incorporation of early Buddhist and Zen Buddhism concepts into the current practice of REBT.