In this paper I will explore a fact that toleration is difficult in complicated ways and this explication will be made with analyses and discussions of the concept of toleration and three approaches to solving the difficulties of toleration. These approaches are quite typical and have been suggested by different scholars. I shall explain how two of them fail to do the work and explain how the third alternative, that is, the moral psychological approach comes to help. The crucial reason for emphasizing the important role of the moral psychological approach is that the psychological aspects of toleration, among other things, give rise to the complicated difficulties of toleration. I explain how the relevant work by John Rawls on moral psychology in political philosophy, especially his idea of the requirement of reasonableness, should shed new lights on the issue of toleration.