Testi agiografici e innografici come fonti «storiche»? Sondaggi e criteri di valutazione nei testi bizantini per san Filippo d'Agira e sant'Ambrogio di Milano

The aim of this article is to show on the basis of which criteria mediaeval hagiographic and hymnographic texts can be used as "historical sources". For this purpose the author has examined the Byzantine sources relating to two saints well-known to him: Philip of Agira and Ambrose of Milan. The case of St Philip makes it possible to analyze in what way and from which perspectives hagiographic and hymnographic sources can be used "historically" within a legendary context which is weak from the historical point of view. On the other hand, the case of St Ambrose makes it possible to verify how the same sources can be considered to be "historical" when they refer to a person about whom ample firsthand historical documentation is available.