“Keep your baby eyes (which are the eyes of genius) on what we don’t know,” pioneering investigative journalist Lincoln Steffens wrote in a beautiful 1926 letter of life-advice to his baby son. And yet the folly of the human condition is precisely that we can’t know what we don’t know — as E.F. Schumacher elegantly put it in his guide for the perplexed, “everything can be seen directly except the eye through which we see.” What obscures those transformative unknowns from view are the unconscious biases that even the best-intentioned of us succumb to.

In Willful Blindness: Why We Ignore the Obvious at Our Peril (public library), serial entrepreneur and author Margaret Heffernan examines the intricate, pervasive cognitive and emotional mechanisms by which we choose, sometimes consciously but mostly not, to remain unseeing in situations where “we could know, and should know, but don’t know because it makes us feel better not to know.” We do that, Heffernan argues and illustrates through a multitude of case studies ranging from dictatorships to disastrous love affairs to Bernie Madoff, because “the more tightly we focus, the more we leave out” — or, as cognitive scientist Alexandra Horowitz put it in her remarkable exploration of exactly what we leave out in our daily lives, because “attention is an intentional, unapologetic discriminator.”

The concept of “willful blindness,” Heffernan explains, comes from the law and originates from legislature passed in the 19th century — it’s the somewhat counterintuitive idea that you’re responsible “if you could have known, and should have known, something that instead you strove not to see.” What’s most uneasy-making about the concept is the implication that it doesn’t matter whether the avoidance of truth is conscious. This basic mechanism of keeping ourselves in the dark, Heffernan argues, plays out in just about every aspect of life, but there are things we can do — as individuals, organizations, and nations — to lift our blinders before we walk into perilous situations that later produce the inevitable exclamation: How could I have been so blind?

Heffernan explores the “friendly alibis” we manufacture for our own inertia — the same ones fueling the “backfire effect” that explains why it’s so hard for us to change our minds. She writes in the book:

Whether individual or collective, willful blindness doesn’t have a single driver, but many. It is a human phenomenon to which we all succumb in matters little and large. We can’t notice and know everything: the cognitive limits of our brain simply won’t let us. That means we have to filter or edit what we take in. So what we choose to let through and to leave out is crucial. We mostly admit the information that makes us feel great about ourselves, while conveniently filtering whatever unsettles our fragile egos and most vital beliefs. It’s a truism that love is blind; what’s less obvious is just how much evidence it can ignore. Ideology powerfully masks what, to the uncaptivated mind, is obvious, dangerous, or absurd and there’s much about how, and even where, we live that leaves us in the dark. Fear of conflict, fear of change keeps us that way. An unconscious (and much denied) impulse to obey and conform shields us from confrontation and crowds provide friendly alibis for our inertia. And money has the power to blind us, even to our better selves.

One of the subtlest yet most pervasive manifestations of our willful blindness is our choice of mates. Data from 25 million online dating site questionnaires reveal that “we mostly marry and live with people very like ourselves” — a finding that Heffernan points out always annoys people:

We all want to feel that we have made our own choices, that they weren’t predictable, that we aren’t so vain as to choose ourselves, and that we are freer spirits, with a broader, more eclectic range of taste than the data imply. We don’t like to feel that we’re blind to the allure of those who are not like us; we don’t like to see how trapped we are inside our own identity. […] We like ourselves, not least because we are known and familiar to ourselves. So we like people similar to us — or that we just imagine might have some attributes in common with us. They feel familiar too, and safe. And those feelings of familiarity and security make us like ourselves more because we aren’t anxious. We belong. Our self-esteem rises. We feel happy. Human beings want to feel good about themselves and to feel safe, and being surrounded by familiarity and similarity satisfies those needs very efficiently.

And yet, she notes, our minds work much like the dating site algorithms — we scan life for matches and, when we find one, we relish the feel-good affirmation. It’s just one manifestation of our soft spot for “filter bubbles,” exploited by everything from Amazon’s book recommendation engines to the elaborate audience-tailoring of modern media. (Heffernan touches on the big-picture disservice in the media’s insidious practice of narrowing our horizons for profit, rather than expanding them in the public interest: “[Media companies] know that when we buy a newspaper or a magazine, we aren’t looking for a fight… The search for what is familiar and comfortable underlies our media consumption habits in just the same way as it makes us yearn for Mom’s mac ’n’ cheese.”) She captures the dark side:

The problem with this is that everything outside that warm, safe circle is our blind spot.

Remarkably, these blind spots turn out to have a physical foundation in the brain. Heffernan quotes neurologist Robert Burton, who studies the biological basis of bias and why our brains tend to reject information that broadens our outlook:

Neural networks don’t give you a direct route from, say, a flash of light straight to your consciousness. There are all kinds of committees that vote along the way, whether that flash of light is going to go straight to your consciousness or not. And if there are enough ‘yes’ votes, then yes you can see it. If there aren’t, you could miss it. But here’s the thing: What does your brain like? What gets the “yes” vote? It likes the stuff it already recognizes. It likes what is familiar. So you will see the familiar stuff right away. The other stuff may take longer, or it may never impinge on your consciousness. You just won’t see it.

Burton illustrates this with a beautiful, if unsettling, metaphor:

Imagine the gradual formation of a riverbed. The initial flow of water might be completely random — there are no preferred routes in the beginning. But once a creek is formed, water is more likely to follow this newly created path of least resistance. As the water continues, the creek deepens and a river develops.

Over the course of our lives, our accumulation of experiences, relationships, and ideas shapes the proverbial riverbed of the mind, and the water begins to flow with less and less resistance, which in turn produces a sense of certainty and ease that only deepens the riverbed. (In the excellent A General Theory of Love, these coteries of gradually encoded information patterns are elegantly described as “attractors”.) Heffernan contemplates the repercussions:

Our blindness grows out of the small, daily decisions that we make, which embed us more snugly inside our affirming thoughts and values. And what’s most frightening about this process is that as we see less and less, we feel more comfort and greater certainty. We think we see more — even as the landscape shrinks.

Hardly anywhere is our willful blindness more unrelenting than in love. The old adage that “love is blind,” it turns out, has strong psychological roots:

When we love someone, we see them as smarter, wittier, prettier, stronger than anyone else sees them. To us, a beloved parent, partner, or child has endlessly more talent, potential, and virtue than mere strangers can ever discern. Being loved, when we are born, keeps us alive; without love for her child, how could any new mother manage or any child survive? And if we grow up surrounded by love, we feel secure in the knowledge that others believe in us, will champion and defend us. That confidence — that we are loved and therefore lovable — is an essential building block of our identity and self-confidence. We believe in ourselves, at least in part, because others believe in us and we depend mightily on their belief. As human beings, we are highly driven to find and to protect the relationships that make us feel good about ourselves and that make us feel safe.. Those mirrors confirms our sense of self-worth. Love does the same thing … and that seems to be just as true even if our love is based on illusion. Indeed, there seems to be some evidence not only that all love is based on illusion — but that love positively requires illusion in order to endure.

Because of how integral love is to our sense of identity — lest we forget: “Who we are and who we become depends, in part, on whom we love.” — we are remarkably averse to seeing anything that threatens that sense by pulling the virtues of our loved ones into question.

The most harrowing example of this blindness, Heffernan points out, is in families damaged by child abuse. Some 700,000 cases of child abuse are reported each year — and this is one of the most underreported forms of violence in society for a variety of reasons — which makes it impossible to imagine how so many families can be blind to the tragedy within. And yet, Heffernan notes, imagining and acknowledging such a devastating idea requires of non-perpetrating parents and guardians to question their own reality to such a degree that many find unconscious escape in their “willful blindness.”

She returns to the broader phenomenon:

Nations, institutions, individuals can all be blinded by love, by the need to believe themselves good and worthy and valued. We simply could not function if we believed ourselves to be otherwise. But when we are blind to the flaws and failings of what we love, we aren’t effective either… We make ourselves powerless when we pretend we don’t know. That’s the paradox of blindness: We think it will make us safe even as it puts us in danger.

And yet willful blindness, Heffernan argues, isn’t a fatal diagnosis of the human condition — it may be our natural, evolutionarily cultivated tendency, but it is within our capability to diffuse it with the right combination of intention and attention. She reflects on the heartening evidence to which the various studies reviewed in the book point:

The most crucial learning that has emerged from this science is the recognition that we continue to change right up to the moment we die. Every experience and encounter, each piece of new learning, each relationship or reassessment alters how our minds work. And no two experiences are the same. In his work on the human genome, the Nobel laureate Sydney Brenner reminds us that even identical twins will have different experiences in different environments and that that makes them fundamentally different beings. Identical twins develop different immune systems. Mental practice alone can change how our brains operate. The plasticity and responsiveness of our minds is what makes each of us most remarkable… We aren’t automata serving the master computer in our heads, and our capacity for change can never be underestimated. […] We make ourselves powerless when we choose not to know. But we give ourselves hope when we insist on looking. The very fact that willful blindness is willed, that it is a product of a rich mix of experience, knowledge, thinking, neurons, and neuroses, is what gives us the capacity to change it. Like Lear, we can learn to see better, not just because our brain changes but because we do. As all wisdom does, seeing starts with simple questions: What could I know, should I know, that I don’t know? Just what am I missing here?

Willful Blindness is a provocative and necessary read from cover to cover. Complement it with NPR science correspondent Shankar Vedantam’s The Hidden Brain and Rebecca Solnit’s manifesto for welcoming the unknown.