Plato justifies the concentration and exercise of power for persons endowed with expertise in political governance. This article argues that this justification takes two distinctly different sets of arguments. The first is what I shall call his 'ideal political philosophy' described primarily in the Republic as rule by philosopher-kings wielding absolute authority over their subjects. Their authority stems solely from their comprehension of justice, from which they make political judgements on behalf of their city-state. I call the second set of (...) arguments Plato's 'practical political philosophy' underlying his later thought, where absolute rule by philosopher-kings is undermined by the impure character of all political knowledge. Whereas the complete comprehension of justice sanctions the absolute political power of those with this expertise, partial knowledge of justice disallows for such a large investment of power. Plato's practical political philosophy argues for a mixed theory of governance fusing the institutions of monarchy with democracy in the best practical city-state. Thus, Plato comes to realize the insurmountable difficulties of his ideal political thought, preferring a more practical political philosophy instead. (shrink)