Marilynne Robinson asks hard questions. She challenges readers with a severe, sophisticated and spellbinding style and a determination to change the conversation about contemporary American culture. In "Gilead," her 2004 Pulitzer-winning novel, and "Home" (2008), a sequel of sorts, she explored the mystery of existence in exquisite, passionate and painful portraits of the spiritual grasping of fathers and sons.

And now, in "Absence of Mind," based on her Dwight Harrington Terry Lectures at Yale, she takes on "the systematically reductionist conceptual vocabulary" of those who use the authority of science to describe -- and delimit -- human nature. They have stripped away concepts hospitable to religion, she insists, and, by positing a mind radically constrained by biology, have reduced it to "a passive conduit" of purposes over which it has no control.

"Absence of Mind" is important not so much as a brief for religion but as a tenacious and often trenchant critique of modern Western thought. Consider, for example, Robinson's assault on the assumption of neo-Darwinists that because the brain has evolved to maximize the chances of genetic survival by increasing access to food and sex that only self-interest disguised as altruism can account for human behavior. Equating homo sapiens with bees, termites and naked mole rats, she writes, the theory is applied with "great confidence" in deference to a "formula that can never be made subject to any test in a human population."

Equally arresting is Robinson's claim that Freud brought to bear "not reason but rationalization" to his definition of the unconscious. Limiting it to "the few but potent urges of the primitive self," which constituted the "unacknowledged core of frustration and guilt at the center of subjective experience," she claims, Freud undercut the efficacy and power of the self-conscious mind. Although Freudianism has been discredited, she points out persuasively, it still "holds its place among the great, sad epochal insights that we say have made us modern."

Robinson respects "real" scientists. As an inquiry into the nature of reality, she has said, string theory can be as satisfying as theology. Nonetheless, she believes that "it is the soul that appraises what the mind integrates," forcing people to stand apart from themselves in exercises of self-scrutiny and self-doubt. As articulated in "Absence of Mind," this article of faith, not susceptible to proof, and easily lampooned as the product "of acculturation or the fetish of the primitive brain," is well worth a hearing, even from those of us who are not believers.

Glenn C. Altschuler is the Thomas and Dorothy Litwin Professor of American Studies at Cornell University.