Ferrari, G. R. F., ed., The Cambridge Companion to Plato's Republic, New York: Cambridge University Press, 2007.

Excerpt:

When is it that we choose to journey with companions? Most often, I suppose, when we want to make the journey fuller, more pleasant, more vivid. But we may also want a fellow traveler to point out landmarks we might be missing or perhaps to assure us we are headed along the best or safest route to our destination. The companion is not a scout; he does not strike out ahead in order to prepare us for a journey that we have not yet begun. This Companion to Plato’s Republic, accordingly, is not a preparatory book; it is not written to be read in advance of Plato’s Republic, still less instead of it.

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