There is an old story that while the king in Veii was offering a sacrifice, a priest declared that he who carved up the victim's entrails would be victorious in the war; the priest's words were overheard by some of the Roman soldiers in the tunnel, who thereupon opened it, snatched the entrails and took them to Camillus. Personally I am content as a historian, if in things which happened so many centuries ago probabilities are accepted as truth; this tale, which is too much like a romantic stage play to be taken seriously, I feel is hardly worth attention either for affirmation or denial.
When Livy says this, he marks an important distinction between himself and another kind of tale about the past and also he establishes that that kind of tale is one of his sources. Livy's reliance on stories to tell him about the Roman past should come as no surprise- the texture and colour of his narrative is about character and character survives, not through the kinds of senatorial and consular records that Rome might have had of its remote past, but through stories, passed down through the ages. Now Livy in my view understood that such stories had a value- he did not dismiss them but used them within his narrative to flesh it out- and prized the faculty of memory rightly as something that can pass something of the truth down. But he distinguished between what he did and these stories.
That's the next interesting judgement for us to make- what distinguished Livy's art from say a storyteller's art was the distinction that Livy draws immediately in this passage- between the romantic theatre episode and the true history. True History involves everything that the story does- but it involves more- it involves what Livy does to the story- he changes it. He changes it through the agency of reason, through the agency of an assessment of probabilities. He does not merely repeat, but he evaluates. And he evaluates against a standard- not of what will entertain but of what will educate. This difference is key- because is the difference between a student and a story teller. One evaluates a story by reason of its entertaining status- the other suspects entertainment as something that might be embellished- for him it is the detail, the little incident that doesn't fit that sounds credible. Its here that Livy establishes for me his reputation as a historian- not in the decision to include stories but in the decision to reject.
We have a historian here not a folklorist. There are many virtues to a folklorist- but amongst them is not the virtue of being a historian- why should we evaluate someone by that standard who has no wish to be so evaluated. Livy though is not a folklorist- he uses the products of the folklorist, the singer of songs, but evaluates them and places them in his narrative because he believes them to be true. He even places those in his narrative he believes to be false in order to present his reader with a fuller picture. The King of Veii never probably had his sacrifice stolen from him in this way- it would have been a picturesque detail- but Livy the historian sacrificed it on the altar of attempting something else, history.