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 that thought is only important if it can escape those limits. Ideas die; "each concept collapses, eventually, to merge with its opposite, like two waves breaking against each other only to subside into the same line of white foam."…

[Alchemy] was the science of transformation, and Zeno broods long on natural instances of miraculous transformation: not least in the erotic life, and even in the movement of the bowels. He is practical—he builds mechanical looms, devises a kind of napalm, performs blood transfusions (with-out understanding why they are sometimes rejected). He is speculative—a barely credible amalgam of the philosophical interests of the period. But alchemy, combining inseparably the ideas of physical and spiritual transformation, takes precedence over all.

"The Abyss," which provides the title not only of the novel but of its most important chapter, is an alchemical term;… the Work in its dark stage, which is "the most difficult phase of the alchemist's process, the separation and dissolution of substance." It is the moment when the base metal is reduced to a formless chaos so that the spirit of the higher may enter it; but it represents also the moment of the mind freeing itself of "all forms of routine and prejudice." So the novel is about the dark transformation of its hero into a higher kind of man. The alchemists also called this stage the "ruining" of the Work, and it is out of some kind of ruin that intellectual greatness comes.

All this Work, this transformation of the mind, goes on in the alembic of history; its fires are the fires of war and judicial murder. The torments of Tridentine Catholicism and institutionalized Protestantism are compounded by plague epidemics and the weapons of the military. Zeno moves about a stricken world, a scientist and a physician, at once welcome and suspect. His fame grows. We are asked to see his career in relation to that of one of his kinsmen, a soldier-poet, enjoying unspeculatively his active life (this is the least satisfactory element in the novel)….

The Abyss is readable enough as a story, but the story merely serves Mme. Yourcenar's obsessive theme, the maturation of a full man; this time a Hadrian without political power, and in an age nobody would call golden. Such a man transcends his age, and being a new man can see what danger his purely intellectual power may hold for the future; for the connection between science and cruelty will not easily be broken. (p. 8)

[Zeno] is the second deity in this author's cult of the full man, endlessly inquiring, ever skeptical, considerate of the body as of the spirit, of the future as well as the present…. The Abyss is a considerable achievement; years of passionate scholarship and long dedication to an ideal of humanity as limited, yet in the end expressed, by history, went to its making. The author deserves her special place in the story. (pp. 8, 10)