The fact that the tyrant is portrayed in the

Republic

as a melancholic has not received sufficient attention. In the medical and philosophical literature of the fifth to fourth centuries BCE， the word “melancholia” means both depression and fear as well as excitement and mania， which is consistent with Plato’s portrayal of the life of a tyrant. The in-depth analysis of regime change in volumes 8 and 9 of the

Republic

provides a key to understanding the “melancholia” of

the tyrannical personality. The oligarchic， democratic， and tyrannical soul are not ruled respectively by three different types of desire， but rather constitute the different stages of collapse of the ruling order in the soul. In light of Plato’s metaphysical doctrine， this collapse is a process of gradual reduction of “limits” and gradual increase of “the indefinite”. The best regime contains the most perfect geometric ratio or “limits”； as the “limits” gradually decrease， each regime contains a greater degree of “the indefinite” than the previous one. The tyrannical personality is the state where “limits” in the soul disappear and fall into pure infinity. It is this state that explains the dual characteristics of the tyrant personality.