The point [of The Abyss] is to create an image of a fully achieved humanity, of a man mature within the conditions of his time; unapologetic about the passions, undeceived yet never vulgarly incredulous in religion; with a deepening sense of the value of other cultures and a growing perception of historical perspective; with a skepticism recognizable as the lubricant of all intellectual achievement, yet compatible with that respect for faith which, against all the intellectual odds, kept so many adventurous minds on the Catholic side of the debate.

The object is to represent Zeno thus, as a free spirit. Scornful of dogmatic dispute … he nevertheless respects true piety as much as he detests bigotry, and cruelty…. As a free thinker, Zeno understands the most important fact about the history of thought, which is that all epochs are trapped intellectually in a net of opinion and presumption, and...