Who, exactly, was Livy borrowing from when he wrote 24.8.12-13. He would have surely already had this concept in his mind. The source of the metaphor is supposedly Plato’s Republic IV, but I wonder if Livy would have read that? If he’s reading Polybius I suppose he may have been taught Greek philosophy at some stage. He probably would have read Horace Carm 1.14 O navis referent in mare te novi, traditionally titled as “To the Ship of State” but the ship in question could well have been a woman or Horace’s own life, although Quintillian Inst 8.6.44 seems entirely sure the ship in the poem, and its struggles to reach the safe harbour of pace atque concordia (Quintillian’s words), are an allegory for the state. Although I’ll note that Fraenkel, E, Horace 1957 Oxford:Clarendon Press p. 155 fn 4, appears to take umbrage at the notion that Horace’s ode was about Horace’s own life, and usually I prefer to believe Fraenkel’s lucid and learned interpretations of Horace.
Meanwhile, in book 24, Livy has Q. Fabius Maximus use this direct nautical metaphor in a speech about who should be elected the consuls for the next year (214):
quilibet nautarum vectorumque tranquillo mari gubernare potest; ubi saeva orta tempestas est ac turbato maria rapitur vento navis, tum viro et gubernatore opus est. non tranquillo navigamus, sed iam aliquot procellis submersi paene sumus; itaque quis ad gubernacula sedeat summa cura providendum ac praecavendum vobis est. (Livy 24.8.12-13)
While the sea is tranquil anyone of the sailors or passengers is able to helm (the ship); when a savage storm has arisen and the ship is ravaged by winds on a turbulent sea, then the job is for a (real) man and a (proper) pilot. We do not sail in tranquil weather, but recently we have been nearly sunk by several hurricanes; and thus (the question of) who would sit at the helm you ought to guard and give attention to with the highest of care.
The “several hurricanes” being events such as the battles of Trasimene and of course, Cannae.
I am finding it off that something of Cicero’s doesn’t seem to pop up here initially: we go straight from Plato to the poets. I should expect that there’s a rich literature on this metaphor that has somehow bypassed my research so far. Time to correct that.