REBT非常重视理性和非理性。在这种情况下，非理性是任何不合逻辑或以某种方式阻碍个人实现其长期目标的东西。结果，理性没有固定的定义，而是取决于个人的目标以及将帮助他们实现这些目标的因素。 REBT认为，非理性思维是心理问题的核心。 REBT指出了人们表现出的几种特定的非理性信念。这些要求包括：苛刻性或强制性-僵化的信念使人们以诸如“必须”和“应该”之类的绝对术语进行思考。例如，“我必须通过这项测试”或“我应该始终被自己的重要他人爱着。”这些陈述所表达的观点通常是不现实的。这种教条式的思维会使个人麻痹，使他们破坏自己。例如，希望通过测试，但可能不会通过。如果个人不接受自己可能不及格的可能性，这可能会导致拖延和尝试失败，因为他们担心如果不及格会发生什么。
REBT attaches great importance to rationality and irrationality. In this case, irrationality is anything that is illogical or in some way hinders an individual from achieving his long-term goals. As a result, reason has no fixed definition, but rather depends on individual goals and the factors that will help them achieve them. REBT believes that irrational thinking is the core of psychological problems. REBT points out several specific irrational beliefs that people exhibit. These requirements include: harsh or mandatory-rigid beliefs that allow people to think in absolute terms such as “must” and “should”. For example, “I have to pass this test” or “I should always be loved by my important others.” The views expressed in these statements are often unrealistic. This dogmatic thinking can paralyze individuals and destroy them. For example, I hope to pass the test, but it may not pass. If an individual does not accept the possibility that he or she may fail, this can lead to delays and attempts to fail because they are worried about what will happen if they fail.