Origen, Against Celsus 1.42

πρὶν ἀρξώμεθα τῆς ἀπολογίας, λεκτέον ὅτι σχεδὸν πᾶσαν ἱστορίαν, κἂν ἀληθὴς ᾖ, βούλεσθαι κατασκευάζειν ὡς γεγενημένην καὶ καταληκτικὴν ἐμποιήσαι περὶ αὐτῆς φαντασίαν τῶν σφόδρα ἐστὶ χαλεπωτάτον και ἐν ἐνίοις ἀδύνατον. φέρε γάρ τινα λέγειν μὴ γεγονέναι τὸν Ἰλιακὸν πόλεμον μάλιστα διὰ τὸ ἀδύνατον προσπεπλέχθαι λόγον περὶ τοῦ γεγενῆσθαί τινα Ἀχιλλέα θαλασσίας θεᾶς υἱὸν καὶ ἀνθρώπου Πηλέως, ἢ Σαρπηδόνα Διὸς, ἢ Ἀσκάλαφον καὶ Ἰάλμενον Ἄρεος, ἢ Αἰνείαν Ἀφροδίτης· πῶς ἂν κατασκευάσαιμεν τὸ τοιοῦτον, μάλιστα θλιβόμενοι ὑπὸ τοῦ οὐκ οἶδ’ ὅπως παρυφανθέντος πλάσματος τῇ κεκρατηκυίᾳ παρὰ πᾶσι δόξῃ περὶ τοῦ ἀληθῶς γεγονέναι τὸν ἐν Ἰλίῳ πόλεμον Ἑλλήνων και Τρώων;

Before we begin the defence speech, it must be said that undertaking to show that almost any history, even if it is true, actually happened, and to create a mental image about it, is among the very hardest things, and in some cases is impossible. Suppose that someone says the Trojan War did not take place, principally because of the impossible narrative that is interwoven – that Achilles was the son of a sea-goddess and of the mortal Peleus, or Sarpedon was the son of Zeus, or Ascalaphus and Ialmenus were the sons of Ares, or Aeneas was the son of Aphrodite. How could we prove that this is how things were, especially as we would be hard pressed by the fiction that has been stitched (I don’t know how) onto the universally accepted opinion that the war at Troy between the Greeks and Trojans really did take place?