John Updike once pithily summarized most sermons this way: "Raise the doubts, then do the reassurances." Marilynne Robinson's brand of homiletics leaves little room for the second part of that equation.

It's not that she doubts her Christianity in the 17 pieces that make up her fourth essay collection, "The Givenness of Things." That much is rock-solid. But she's determined to destabilize our thinking about faith, be it by elevating religious thinkers such as Jonathan Edwards and John Calvin (misunderstood progressives, to her mind); questioning easy assumptions about God's relationship to sin and science, and facing up to the mystery that's inevitable in faith.

To that last point, she bristles at attempts to make Christianity reassuringly self-help-ish, "push[ing] mystery aside as if it were a delusion of ignorance or fear that can have no relevance to people living in the real world."

For those who know Robinson only from her careful, full-hearted novels about faith and family in Idaho (where she was born) and Iowa (where she lives now), these dense and contemplative pieces can be tough sledding. One essay exploring the theological implications of the "begats" that open the Book of Matthew has the rigor of a div-school lecture; another on the nature of grace in Shakespeare's plays arrives with high expectations of the reader's command of the Bible and the bard.

In some ways, though, this level of erudition is refreshing. Robinson's writing betrays not only deep research but a conviction of the broad importance of her intellectual pursuits, no matter how esoteric. When she expresses her concerns about neuroscience, as she often does, she's exploring a pitched battle about the nature of our self: "Science of the kind I criticize tends to assert that everything is explicable," she writes. But what room is there, she asks, for the soul in constant Fitbit-ification of our lives?

She's blunter still on matters of social justice, despairing of how some corners of American Christianity have rationalized gun ownership, bigotry and contempt for the poor. "There are people who want to pile money on money, but they are the takers, not makers," she writes. "Easily half of the Bible by weight supports me on this point, and nine-tenths of cultural history."

Faith in God she has plenty of; faith in society's improvement on these fronts is limited. "By the standards of, let us say, Renaissance England and Europe, we're really not doing too badly," she concedes. Fair point: If you're reading this, you probably don't have bubonic plague. If that's not much reassurance, tough. Grace and generosity define Robinson's fiction, but this book reveals how much labor goes into understanding them.

Mark Athitakis is a reviewer in Phoenix.