In Book VI of the Republic a grocery list of the desirable traits to be found in a philosopher are described by Socrates.  The list of virtues is long and encompassing: a love of learning of things that are (485b), no taste for falsehood (485c), a concern with the pleasures of the soul, not the body (485d), being moderate and not a lover of money (485e), not given to petty speech (smikrologia) (486a), believing that death is no great evil (486b), being “just and tame not hard to get along with and savage” (486b), learning easily (486c), has a good memory (486c), has measure and charm (486d).

Equally prominent in this discussion of what the virtues are is the continual emphasis that  Socrates places on nature.  We are left to puzzle about what the definition of “nature” is here, a term frequently and problematically employed in philosophical contexts.  The traits listed above are somehow desirable in the philosopher only if they are present by nature.  However, there is little discussion of what nature is, and what we are left with is a view of nature that consists in little more than whatever inborn proclivities one happens to have, as is exemplified in this statement about a man erotic by nature, “It’s not only likely, my friend, but also entirely necessary that a man who is by nature erotically disposed toward someone care for everything related and akin to his boy” (485c). 

This explanation of nature is further corroborated by the foreshadowing of the philosopher first seen in Book II.  There, Socrates and Glaucon agreed that they were looking for a chimerical kind of guardian, one who is, “at the same time gentle and great-spirited.  Surely a gentle nature is opposed to a spirited one”  (375c).  When they deliberate further upon this discovery, Socrates and Glaucon despair, since the combination of two opposed traits would appear to be a contradiction.  However, soon Socrates realizes that, “You know, of course, that by nature the disposition of noble dogs is to be as gentle as can be with their familiars and people they know and the opposite with those they don’t know”  (373d).  The explication of this “noble dog,” analogous to the philosopher, is telling, because it will inform us not only about Plato’s conception of nature here, but by extension the nature of the philosopher.  Socrates explanation of the dog’s behavior is not in terms of training, but something rather more inborn: “When it sees someone it doesn’t know, it’s angry, although it never had any bad experience with him.  And when it sees someone it knows, it greets him warmly, even if it never had a good experience with him”  (376a).  Thus it is not by training that the dog has learned to embody a composite of two opposed traits, for this would be impossible.  Furthermore, as Socrates analysis makes clear, the dog’s nature makes it immune to any training by experience which it could have undergone.  It is friendly to its owner by nature, and hateful to strangers by nature despite any exposure intentional or unintentional which could train the dog to behave in exactly the opposite way.  Thus when we are told that the philosopher is to hold certain traits by nature, this is to say that he should be possessed of these traits from birth, which manifest themselves in a disposition that easily expresses them.

Note: All translations from Allan Bloom, The Republic of Plato.