Common sense may not be so common, but what exactly is it and what is it for? Aristotle thought there must be a special sense to coordinate the other senses. This meaning persisted through the Middle Ages, although the Romans had added another meaning: a moral sensibility shared with others. It fell to Descartes to provide the modern meaning of “good sense” (bon sens) or practical judgment. Like the other senses, he thought it was not reliable and should be supplemented by formal reasoning. Giambattista Vico, the father of sociology, thought common sense was not innate and should be taught in school. His view of it as judgments or biases, held in common by a society, merges with the idea of public opinion or consensus. Kant and later thinkers returned to the idea of a shared moral sensibility, so that common sense is related conceptually and linguistically to conscience.

We have long taken common sense for granted, that it should come as standard equipment with each human being. That presumes, however, that each person not only develops according to a norm but develops in the setting of the real world. Ultimately, it is physical reality and our physiology that we have in common, which provide the biological basis for mutual understanding and consensus. The human organism, like all others, evolved as an adaptation to the natural world. Whatever “practical judgment” we have is learned in relation to a world that holds over us the power of life and death. Common sense is our baseline ability to navigate reality.

Of course, most of us do not grow up in the wild, like animals, but in environments that are to a large degree artificial. “Reality” for us is not the same world as it was for people a hundred years ago, a thousand years ago, or ten thousand years ago. Yet, until recently, the reality experienced by people of all times lay objectively outside their minds and bodies. Common sense was firmly grounded in actual sensory experience of the external world. This can no longer be taken for granted. We now live increasingly in “virtual” realities that are, however, far from virtuous. Because they can be as diverse and arbitrary as imagination (now augmented by AI) permits, there is no longer a common basis for shared experience, or for common sense.

This shift is the latest phase of a long-standing human project to secede from the confines of nature and the body. In the anthropological sense, culture is the creation of a distinctively human realm, a world apart from the wilderness and physical embodiment. We built cities for physical escape. Our first mental escape was through trance, drugs, and religion, which imagined a life of the spirit or mind that was distinct from the life of the animal body. With Descartes, “private experience” formally became a realm unhooked from the external world. With dawning knowledge of the nervous system, he grasped that the natural formation of experience could be hijacked by a malicious agent. His thought experiment became the basis of the “brain in a vat” scenario, the Matrix films, and the paranoid popular memes that you are “probably living in a simulation” or in a theatrical hallucination created by “prompts.” Descartes consoled us that God would not allow such deception. Humanists supposed that natural selection would not allow it. Post-humanists invite it in the name of unlimited freedom.

In any case, common sense is the baby thrown out with the bathwater of external reality. Through technology, humanity grants itself its deepest wish: to be free to roam in inner man-made worlds disconnected from the world outside the skull. Nature had granted us a relative version of that freedom through dreaming and imagination. But our impulse toward creative mastery requires that humanity find this freedom on its own, not naturally but artificially. It must be created from scratch, originally and absolutely, not accepted as a limited hand-me-down from biology. Here we venture into dangerous territory. For, we continue to be vulnerable embodied creatures living in real reality, even as we buckle up for the virtual ride. Is God looking out for us while we trip? Is nature? The other side of utter creative freedom is utter self-responsibility. If experience is no longer to be grounded in the real world, but a matter of creative whim, then what basis is there for limits and rules—for anything but chaos?

The more time children spend online, using their eyes to look at screens instead of at the world outdoors, the less direct experience they will have of the external world. The more time they spend in some entertaining digital fantasy, the less basis they will have for developing their own common sense, which is grounded in the natural use of the senses to explore the external world. Of course, this applies to adults as well. It is not only the proper use of the senses that may atrophy, but the very ability to distinguish real from virtual, nature from artifact, truth from lie. The contents of movie entertainment, for example, are often absurdly fantastical, about themes and situations deliberately as far removed as possible from the tame humdrum of real life. It is precisely drug-like distraction from daily living that entertainment is typically designed to provide. But this is a vicious circle. We then expect from the real world the level of stimulation (adrenaline, serotonin?) that we get artificially from films, online gaming, “adult” content, and “substance abuse.” Indeed, we are trained to ignore the difference between reality and fiction, which can result in failure to tell the difference.

Social media are a form of entertainment, a virtual drug in which truth is reduced to gossip. They may help build consensus with those who “like” you and are like you in some context. In a brave new world of information overload, where the basic challenge is to sort what is fact or reliable opinion from what is not, common sense should be a legacy tool one can count upon. But common sense is not consensus. The failure of a society to know the difference is the banal soil in which authoritarianism grows. We are seeing it around the world right now.

Large language models and similar “generative” tools are another form of virtual reality and entertainment. Ironically, if properly used, they provide access to an artificial version of common sense—or at least consensus. For, they draw upon the common pool of human experience and creative output, as archived digitally. The answers you get to chatbot queries reflect a baseline of collective human knowledge and creativity; they are also organized according to collective ideas about what is logical, sensible, relevant. Another name for such collective wisdom, however, is mediocrity. LLMs are not minds that can think for themselves or originally. If they regurgitate information that proves useful to you, the task of understanding and using the information remains your own, grounded in common sense.

The internet potentially embodies the ancient ideal of omniscience. In itself, the instant online access to encyclopedic knowledge aggravates the problem of discernment: how to know what and whom to trust. The traditional answer to that dilemma has been education, reinforced by common sense, what is meaningful and what is chaff. The traditional encyclopedia, while vetted by well-educated experts, gives relatively cursory information. The new answer is the “intelligence” of the AI tool itself, which sifts, organizes, and even interprets seemingly unlimited information on your behalf. You place your trust in it, as you would in human experts, at your own risk. It draws upon a common denominator of expert opinion. As with human experts, however, you are still dealing with hearsay: accounts that are second-hand (or nth-hand), which you must interpret for yourself. When your quest to go deeper approaches the ceiling of current common understanding, the replies will simply recycle existing clichés.

The situation is like what happened with the invention of printing. Suddenly people had a greatly expanded access to information (beginning with the Bible). This invited them—and indeed required them—to think for themselves in ways they were not used to when guided by the erstwhile gatekeepers of knowledge. This hardly led to consensus, however, but to an explosion of diverging Protestant sects. An optimistic view of the new information revolution is that people are similarly being challenged to think for themselves. Again, the actual result seems to be divisiveness. Of course, the printed page—while novel, thought provoking and entertaining—did not do people’s thinking for them. Yet, AI proposes do exactly that! To implicitly trust the authority of AI is not so different from the faith in religious authority before the Reformation, when the priest could do your thinking for you. If common sense did not provide immunity from the excesses of theology, we can blame the closure of the medieval  world—an excuse we should no longer have. Common sense should be the back-up tool of first resort. But to maintain it requires first-hand experience in the real natural world, which you cannot get online.