That same year, as the result of an earthquake or some other violent upheaval, it is said that the middle of the Forum or thereabouts collapsed, leaving a huge chasm of enormous depth. The abyss could not be filled by throwing in the earth which everyone brought, until a warning from the Gods started the people wondering what was the chief strength of the Roman people; for that was what the soothsayers declared must be offered up to the place, if they wished the Roman Republic to endure forever. At this time (as the story goes) Marcus Curtius, a young man of great military distinction, rebuked those who doubted whether Rome had any greater asset than her arms and valour. In the silence which followed he looked up to the temples of the immortal Gods which tower over the Forum and the Capital, and stretching out his hands now to the heavens, now to the yawning gulf in the ground and the Gods of the underworld, he devoted himself to death. He then mounted a horse caparisoned with all possible splendour and plunged fully armed into the chasm. A crowd of men and women then threw piles of offerings and fruits of the earth in after him. Curtius's pool was named after him, it is said. (VII 6)The death of Marcus Curtius was a particularly grisly one- what Livy does not tell you is that the young soldier died either from the shock of the plunge or worse from being buried alive. That concealment is not though the most interesting point of the story- for the story brings to light two issues- the first is Livy's practice as a historian, the second is Livy's intention within his history. Let us take the first first, why is Livy telling us this story? He expresses in two places in the above passage a caution to his readers- this is a story, it is a tradition, so antique that 'certainty [is] impossible' (VII 6). The historian must though pay attention to an aural tale- it is not possible merely to dismiss it as it may conceal something of truth, the fact that the name of the pool is 'better known from the more recent legend' (VII 6) is evidence that it possibly owes its origin to something like this incident. Though Livy has to make this judgement to complete his narrative, he has to also offer his readers the reminder that the story is a story- it is not certain, it is doubtful.
A historian does not merely ascertain truth, he also selects what to include and what not to include. Why does Livy include this story? Firstly I suspect he included it because it was interesting and dramatic- it aids the narrative construction of his history, it keeps the reader's interest in a ghoulish way (afterall a young man is being buried alive). That however is not the only reason that Livy selects this story to tell us- the centre of the tale is the prophesy of the soothsayers that if Rome throws into the hole its chief strength it will survive forever. Curtius interpreted that as being the military might that Rome possessed and threw himself as a good soldier and representive of that might into the gap. The soothsayers suggest not merely that Rome will survive forever but that the Roman Republic will survive forever- Livy though offers no comment on Curtius's actions or the soothsayer's prophesies. The interesting question to ask is whether he believed Curtius was right- he leaves the answer ambiguous for a political reason (to question whether the Republic had survived into the reign of Octavian might be dangerous) and also to leave us guessing about what the heart of the Republic's survival might be.
Curtius definitely gets something right in Livy's view. Military valour was part of the heart of the Roman Republic- authors from Livy to Gibbon were to laud the martial virtu of the Roman soldier- but the key issue here is whether that was a cause or consequence of the virtue of the Republic. Stepping back I think it is clear to say that it was a consequence- and that Livy himself may well have said that- we have seen in other contexts that Livy believed (as did other Roman authors) that victory was potentially destabilising. War allowed the plebeian party to destabilise the state and use its threat of a strike to intimidate the patricians. War brought in foreign luxuries to the state- corrupting the pure and simple tastes of the Republic. Furthermore had the Republic survived forever? What is interesting about this story is it furnishes us with an ironic comment on what will later happen- on the story that Livy will tell, the triumph of the Republic through war and its destruction through conquest- Curtius's fate points to the error that Rome will later make, to imagine that if the form of government survives, its reality survives as well. That if Rome's armies are strong then Rome herself is strong- Livy's theme is in part a rejection of that- a rejection of the idea that a large despotism is better than a small republic.
Ultimately Curtius's behaviour is an episode of republican virtue but not of Republican wisdom- by throwing in Roman martial valour (and this may be an interpretation too far) Livy may be suggesting that Curtius secured the survival of the Roman state, but not the Roman Republic.