In his "Author's Apology" at the beginning of Pilgrim's Progress, Bunyan uses ethos, or an appeal to authority, to persuade readers that his use of metaphor and allegory is acceptable:
The Prophets used much by Metaphors
To set forth Truth; yea, whoso considers
Christ, his Apostles too, shall plainly see,
That Truths to this day in such Mantles be.
Am I afraid to say that Holy Writ,
Which for its Stile and Phrase puts
down all
Wit,
Is everywhere so full of all these things,
Dark Figures, Allegories? Yet there springs
From that same Book that lustre, and those rays
Of light, that turns our darkest nights to days.
Bunyan anticipated that readers might object to his use of metaphor and allegory as too fanciful and obscure for a book dealing with the subject of the soul's salvation. Surely, their argument might go, such a life-and-death subject calls for the plainest language, not for imaginative storytelling.
In response, Bunyan turns this argument on its head by pointing out that the Bible itself uses metaphor and allegory—quite a bit, in fact. The books of the Old Testament prophets are replete with vivid metaphors illustrating God's judgment and redemption of his people. Not only that, but "Christ, his Apostles too," dressed their teachings in the "Mantles" of metaphorical language, such as Jesus's parables and, for instance, Paul's allegorical application of Old Testament figures (like Sarah and Hagar) and events (like Noah's ark) to Christian doctrine. Given that the Bible, the written authority for Protestant belief, is filled with such language, then Bunyan must be permitted to use "Dark Figures, Allegories" for religious purposes, too. After all, the Bible sends forth "rays / Of light" that clearly enlighten readers to spiritual truth, no matter how obscure and figurative some of its language. Bunyan well knew that nearly anyone who took up Pilgrim's Progress in the late 17th century would hold the Bible in highest esteem; so, his use of ethos to bolster his own use of figurative language and allegory is both sincerely meant and pointedly targeted.
