I think so.

And who is best able to do good to his friends and evil to his enemies in time of sickness?

The physician.

Or when they are on a voyage, amid the perils of the sea?

The pilot.

And in what sort of actions or with a view to what result is the just man most able to do harm to his enemy and good to his friend?

In going to war against the one and in making alliances with the other.

But when a man is well, my dear Polemarchus, there is no need of a physician?

No.

And he who is not on a voyage has no need of a pilot?