"To be virtuous, and to be a lover of wisdom (a 'philosopher'), are one and the same." --Plato
Philosophers are people who do such-and-such (read books, engage in dialectic, study at the Academy, know that Forms exist). People like that, and only people like that, are genuinely virtuous.
People who do what is just, moderate, courageous, and sagacious are, to that extent, lovers of wisdom (even if they don't know it).
Which did Plato hold? Four arguments that, at least, he would not exclude the broad view:
1. The broad sense is closer to the original sense of 'philosophy'. For Socrates, exhorting to virtue and exhorting to philosophy were the same.
2. The broad sense matches Plato's proclivities elsewhere. His tendency is to interpret activity broadly and generously, as 'really' conforming to and illustrating the philosophical view he favors. Cp. the Symposium:
"To be a poet, and to strive for immortality, are one and the same."3. Plato often regards virtue as conformity to a quasi-mathematical, divine harmony (e.g. Gorgias 508a), and no specialized knowledge would ostensibly be required for this. He takes virtue in the ordinary sense to be the conformity of action and character with this order.
Narrow (not Plato):
People who write poetry and only these are striving for immortality.
Every creature without exception is in some way a 'poet'.
4. If only philosophers were virtuous, we could never learn what words like 'courage' and 'moderation' meant, and the recommendation that philosophy should be pursued, because it makes people virtuous, would make no sense.
The upshot: just as virtue admits of degrees, so 'love of wisdom' admits of expansion. From:
Virtuous iff a philosopher.One can reason, either (as Bobonich does, which, I believe, is not Platonic):
Not a philosopher (in the narrow sense); therefore, not virtuous (in any sense).
Virtuous (in an ordinary sense); therefore, a philosopher (without knowing it).