Happiness, Justice, Harmony

The motor of the Republic is the question 'Is a just person happy?'.  Plato's response is not merely affirmative, but, more resoundlingly, that only a just person is happy.  The basis of that response is the thesis that Justice and Happiness are one and the same: Harmony.  In the Republic, that thesis is grounded in the Idea of the Good, a more concrete version of which is likely the concept of a World-Soul, which he presents in the Timaeus. Now, left unexplained in such Holism is the possibility of unhappiness, but implicit in the Republic is that it is a Political problem, as opposed to a Psychological problem in an Atomist system.