Believe Nothing You See

The ability to intuit object permanence—the idea that things do not cease to exist just because we can no longer see them—is a key cognitive milestone for human infants. Well before 12 months of age, children come to understand that when their red ball rolls behind the couch, it is still there, just out of sight. This understanding is a sign that a child has learned how the physical world works.

But what if it’s not how the world works? What if the baby should instead learn to doubt his perception of the ball in the first place, because neither he, his parents, nor any other sentient creature actually has any idea about the true color, shape, texture, or dimensionality of the object their eyes and brain compute as “ball”?

In his entertaining, mind-disrupting book, The Case Against Reality, University of California, Irvine cognitive scientist Donald Hoffman challenges readers to follow him into a world—for him, the “real” world—in which all of our perceptions are mere hunches devoid of objective truth.

Hoffman argues that humans’ representations of reality contain only enough information to maintain safety and reproductive fitness. It’s a long way to go, but he is as clear-eyed a guide as one could hope to have to the end of the world as we know it. Even while addressing the headiest possible topics, Hoffman writes more clearly and directly than many peers covering more terrestrial subjects.

At the core of his case against our version of reality are two concepts Hoffman has previously introduced into the field of cognitive science. The first is Fitness Beats Truth, or the idea that natural selection does not favor veridical, or true, perceptions but in fact may help drive them to extinction. The other is the Interface Theory of Perception, which suggests that our senses have evolved to represent the physical world around us in a graspable, accessible way—the equivalent of icons on a desktop screen: “Something exists independent of us,” Hoffman claims, “but that something doesn’t match our perceptions.”

On nearly every page, Hoffman presents readers a moment when they will be convinced that he has gone too far—and another in which he somehow reels them back in. After a thorough thrashing of our senses, for example, our thoughts can’t help but turn to human feats like fine tailoring, ocean navigation, and precision manufacturing. How are the pyramids possible if our perceptions are unreal? First, Hoffman reassures, our core mental capacities, such as logic and mathematics, may be just as impressive as we imagine: “It is too simplistic, and false, to argue that natural selection makes all of our cognitive faculties unreliable.”

But, then, don’t our advances in medicine and technology prove that our perceptions of reality have at least evolved to bring us closer to the truth? Not at all. Our ever-more-skillful manipulations of our interface with the world are comparable to the steps it takes to become a successful Minecraft player. We can make incredible things out of the icons our senses put before us, but it doesn’t mean we’re perceiving the actual data that drive them: “Prowess is just prowess, not truth,” Hoffman writes, and brings us “no closer to seeing reality as it is.”

And if no human has a veridical representation of objective reality, then how can we work together to construct a salad, a house, or an aircraft carrier? It’s no problem: Just as we can team up to play Grand Theft Auto in an artificial reality, so we can in the shared perception of reality our senses have evolved to present us.

Some elements of Hoffman’s case against our five most familiar senses as honest agents will be familiar. We already understand, for example, that human vision fills in gaps in what’s before us. And we know that other animals—insects, birds, fish, reptiles—see, hear, and smell a very different version of the natural world; we quite literally don’t know what we’re missing. “Our perceptions are an interface specific to our species,” Hoffman writes. “To declare that humans are the standard is parochial.”

The question, Hoffman writes, is not whether our version or the fly’s is more correct. That’s unanswerable. All we can presume is that each creature’s senses have evolved in a way that promotes its survival and fitness over any objective truth. Our senses, for example, make us recoil at the notion of consuming feces; a rabbit’s lead the creature to the pile.

Human senses also regularly prove that, whether or not they perceive truth, they do promote fitness. We can’t see, touch, or smell oxygen, but our bodies give us a headache or make us lightheaded if there is too little around us, or too much. Similarly, ultraviolet radiation is wholly invisible to us, but when we experience too much, our bodies respond with a sunburn. If our bodies had evolved with the primary mission of showing us the world, and not preserving our fitness, we’d already be extinct. Instead, Hoffman writes, they “hide the truth and display the simple icons we need to survive long enough to raise offspring.”

Even the media of our perception are arbitrary. There could be countless other means of perception that would let us to interact with the world better than we currently can; we just don’t know what they are. We can’t even conceive what it would be like to experience the world with the sonar of a bat or the tentacles of a cephalopod.

What we do understand about our senses, Hoffman believes, only supports his case that our reality is constructed. If the brain is a computational engine, then the task of its visual cortex is the same as your laptop’s when it opens a photo: Take the data from your 130 million photoreceptors, none of which alone provides anything of meaning, and assemble them into an image you can understand. This is not remotely the same as “seeing” objective reality. Vision is an active, constructive process that necessarily separates us from objects in the world, not one that invites us in.

Hoffman’s fealty is to Darwinism—specifically, the more abstract concept of Universal Darwinism, in which natural selection can be applied on a cosmic and microcosmic scale—and not to what his own eyes and hands tell him. His arguments are consistently well reasoned, even if one is wary of following him into such thought exercises as what might happen when a cat is sent hurtling into a black hole.

That conundrum emerges as Hoffman brings the lessons of Fitness Beats Truth and the Interface Theory of Perception to the realm of quantum physics in the chapter that perhaps takes readers farthest behind the putative curtain. (That’s no small statement when considering a book that devotes space to questioning whether we can actually be sure that we live in a three-dimensional, and not a two-dimensional, world.)

Einstein said, “Time and space are modes by which we think, and not conditions in which we live.” Hoffman, citing the later physics concept of Quantum Bayesianism, posits that no measurement can ever reveal an objective truth, because it will always be skewed by the beliefs and perceptions of its measuring agent. That rule, he believes, is consistent with evolutionary biology, which suggests that our own gauging of time, space, and objects is skewed by our senses to enhance our safety and reproductive fitness. “When two pillars of science side with each other, and against our intuition, it’s time to reconsider our intuition,” Hoffman insists. “Spacetime and objects are simply a coding system for messages about fitness.”

Hoffman wants to help readers remove the virtual-reality headset “you didn’t know you were wearing.” What happens after it comes off is less clear, but, he believes, objective reality is not necessarily forever beyond our grasp. A deeper understanding of consciousness could one day bring us closer. Until then, “the probability is zero that we see reality as it is.”