Are people born with a moral sense? If there is one question that lies at the intersection of philosophy and developmental psychology, this is it. Aristotle was one among several ancient philosophers who pondered it. Many years later, so did Charles Darwin, writing about the gradual expansion of his son’s “moral emotions” in “A Biographical Sketch of an Infant,” published in 1877 in Mind.In his book Just Babies: The Origins of Good and Evil, Paul Bloom, a developmental psychologist at Yale University, finds fertile ground in this meeting of disciplines. His contribution to the nature versus nature debate begins with his research at the Infant Cognition Center at Yale, but soon expands to include meditations on moral philosophy and its relationship to various scientific inquiries on topics like racism, disgust and family loyalty.

Bloom was first compelled to write Just Babies after a series of studies on infants produced unexpected results. For one of the studies, he and his colleagues (his wife Karen Wynn and other researchers at Yale’s infant lab) created one-act puppet shows, featuring a main character trying to climb a hill, a second character who helps the main character with his climb and a third character who tries to push the main character down the hill. The researchers wanted to see whether their infant subjects showed a preference for the helper over the hinderer. They did. “What we found is that kids, even before their first birthday, show this quite surprising moral sophistication, the ability to separate right from wrong,” Bloom says.

Proof that babies aren’t “blank slates or meatloaves,” as Bloom terms it, is an interesting enough point of departure for a book. But Just Babies really picks up when Bloom complicates this initial picture of the origins of our morality. For most of the book, Bloom attempts to shed light on a hotly debated topic among philosophers and psychologists—what he describes as “the interplay between our innate understanding and morality; our built-in gut feelings and responses and our intelligence and wisdom.” 

Bloom primarily contributes to this discussion not with any one groundbreaking insight, but by putting scientific studies in conversation with non-scientific discourse. Bloom’s favorite source, in fact, is not a scientist but the philosopher Adam Smith. “He anticipated so much of what we now find through various scientific methods, but at the same he has this wonderful, lyrical prose that I can’t resist quoting quite a bit,” Bloom says.

He always associated the philosopher with the idea of selfishness, based on his reading of Smith’s signature work The Wealth of Nations. But a few yearsbloom cover ago, while spending a summer in Edinburgh, he picked up Smith’s first book, The Theory of Moral Sentiments. “I thought it was magnificent,” Bloom recounts. “A clear-headed and thoughtful analysis of our everyday sense of right and wrong. He talks about revenge, about family, about gratitude, about how we think about rich people and about poor people.”

A definition of morality—what right versus wrong actually means—is not a simple thing to provide. Bloom valiantly attempts to do it. One way he gets at the issue is by discussing our tribal instincts, using his and other researchers’ scientific work to support a case that it comes naturally to people to “carve the world into us versus them.” Babies have a stronger sense of compassion and justice than you might expect, but also show inborn prejudice. A research team at the University of Chicago discovered that babies react differently to people who speak a different language than their mother tongue or who speak their mother tongue with an accent. Adults are much more tribal than babies, though. As various studies in Bloom’s book reveal, we often put people into the “other” category based on skin color, sexual preferences, how people smell and whether or not they are family. “But there the story has to do with what sort of cuts we make, and how as intelligent beings we respond to these intuitive divisions,” Bloom says. This is where his passion for certain Enlightenment philosophers comes into play; Bloom ultimately believes that we can override our base instincts with reason.

“There’s a trend by smart people like Malcolm Gladwell and David Brooks that emphasizes the importance of the emotions, of gut feelings,” Bloom says, describing the broader implications of his argument. “I think this has been overstated. A careful look at our moral lives suggests rationality, and deliberation plays a huge role.” For Bloom, the fact that people are not born with completely developed moral faculties makes society’s moral accomplishments even more extraordinary. In the end, our moral lives are largely up to us. “I want to provide an alternative to a very cynical view of human nature that says we are prisoners of our feelings and thinking is irrelevant,” he says. “I want to suggest that part of the story of morality is rooted in human intelligence.”  

Alexia Nader is a freelance writer and an associate editor at The Brooklyn Quarterly. She has also contributed to Oxford Americanthe New Yorker, and Los Angeles Review of Books.