Desjardins, Rosemary, Plato and the Good: Illuminating the Darkling Vision, Boston, MA: Brill Publishers, 2004.

Excerpt:

Named for a young man whose contribution to the dialogue is largely significant silence, the Philebus explores the notion of good in the context of human life. But right away we run into difficulty. It turns out that, for the Greeks as for us, there is built-in ambiguity in the notion of “the good life”. It will be this very ambiguity which Plato proceeds to exploit as springboard for his inquiry into good—the good life, the human good, or human happiness.

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