What is knowledge? What is the difference between just thinking that something is true and actually knowing that it is? How are we able to know anything at all?
These questions are ancient ones, and the branch of philosophy dedicated to answering them — epistemology — has been active for thousands of years. Some core questions have remained constant throughout this time: How does knowledge relate to truth? Do senses like vision and hearing supply us with knowledge in the same way as abstract reasoning does? Do you need able to justify a claim in order to count as knowing it?
Like many resources, knowledge can be acquired, used for diverse purposes, and lost — sometimes at great expense. But knowledge has a closer connection to us than resources like water or gold. The continued existence of knowledge depends on the existence of someone who knows.
As you put the box down, the coin inside the box has landed either heads or tails: let’s say that’s a fact. But as long as no one looks into the box, this fact remains unknown; it is not yet within the realm of knowledge.
Knowledge demands some kind of access to a fact on the part of some living subject. Without a mind to access it, whatever is stored in libraries and databases won’t be knowledge, but just ink marks and electronic traces. In any given case of knowledge, this access may or may not be unique to an individual: the same fact may be known by one person and not by others. Common knowledge might be shared by many people, but there is no knowledge that dangles unattached to any subject. Unlike water or gold, knowledge always belong to someone.
Or we can say that a rogue nation knows how to launch a nuclear missile even if there is no single individual of that nation who knows even half of what is needed to manage the launch. Groups can combine the knowledge of their members in remarkably productive (or destructive) ways.
What if “knowledge” is nothing more than a label we apply to the attitudes of the elite? In our culture, perhaps a Nobel Laureate’s scientific research or a CEO’s thoughts about his industry; in other times and places, the teachings of the high priest or the tribal elders. Across the board, the thoughts of underdogs get brushed off as superstitions and misconceptions. On this view — call it the Cynical Theory — whether someone’s idea counts as knowledge or mere opinion would be determined by his status as a leader or a loser, and not by anything in the idea itself or its relation to reality.
But the Cynical Theory says something more than that power and knowledge often go together, or are widely thought to go together: it says that there is nothing more to knowledge than the perception of power.
We’ll assume in what follows that truth is objective, or based in reality and the same for all of us. Most philosophers agree about the objectivity of truth, but there are some rebels who have thought otherwise. Protagoras held that knowledge is always of the true, but also that different things could be true for different people. Standing outdoors on a breezy summer day and feeling a bit sick, I could know that the wind is cold, while you know that it is warm. Protagoras held that truth is relative to a subject: some things are true for you, other things are true for your best friend or true for your worst enemy, but nothing is simply true.
Or is it even something that you really read, as opposed to something that you are just now dreaming you once read? If you can’t find any sure way of proving that you are now awake, can you really take your sensory experience at face value?
The Pyrrhonians suggested that behavior can be guided by instinct, habit, and custom rather than judgment or knowledge: in resisting dogma, skeptics do not have to fight against their raw impulses or involuntary impressions. Skeptics can satisfy their hunger and thirst on autopilot while refraining from judgment about reality.
Descartes’s best-known work, Meditations on First Philosophy, presents truly novel skeptical arguments about the limits of reason, alongside familiar ancient arguments about dreaming and illusions. In his deepest skeptical moment, Descartes invites you to contemplate a scenario in which a powerful evil demon is dedicated to deceiving you at every turn, not only sending you illusory sensory impressions, but also leading you astray each time you attempt to make an abstract judgment such as a simple arithmetical calculation.
But however well that strategy might work to dispel particular doubts about artificial limbs, Moore does not think that there is an all-purpose strategy for proving that you hand exists, a general proof that would dispel all possible doubts. The range of possible doubts is truly enormous.
The strategy of declaring that one has knowledge without proof may set off some alarm bells (is More declaring victory after refusing to fight?). It may also seem odd that Moore is willing to construct what he thinks is a very good proof of the claim “External objects exist,” while simply turning his back on the project of proving the somewhat similar claim “These hands exist.”
By contrast, an ordinary claim like “Here is a hand” is so basic that it is hard to find simpler and better-known claims we could use to support it. (There is a parallel with mathematics here, where some basic claims are taken as axioms, not themselves in need of proof.) If the skeptic attempts to undermine our certainty about such basic matters, More would urge us to distrust the skeptic’s fancy philosophical reasoning well before we distrust our original common sense.
From our perspective outside the vat, we’d say that the BIV is virtually holding a virtual book, but from within, the BIV is right to say and think that it is holding a book: its words have meanings appropriate to its environment, and given those meanings, what the BIV believes is true. In fact, nothing stops the BIV from knowing that it is holding (what it would call) a book. The “skeptical scenario” doesn’t really threaten everyday knowledge at all.
On this way of thinking, a VR that is ultimately computational in character is no worse than a physical reality that is ultimately composed of subatomic particles. We might be momentarily unsettled to hear that the ultimate nature of things is stranger than we had previously imagined, but the news should not shake our faith in our ordinary knowledge about shoes, hands, and books.
One way to defend yourself against skepticism is to come up with a diagnosis of why it seems so appealing, despite its tendency to lead us toward strange or even absurd conclusions. Skepticism initially looks appealing (despite its bleak consequences) because it is a good thing carried too far. The good thing is that we have a healthy critical ability to double-check individual things we believe by suspending judgment in them temporarily to see whether they really fit with the rest of what we know. But if this ability to suspend individual beliefs serves as a useful immune system to weed out inconsistent and ungrounded ideas, skepticism is like an autoimmune disease in which the protective mechanism goes too far and attacks the healthy parts of the organism. Once we have suspended too much — for example, once we have brought into doubt the reality of the whole outer world — we no longer have the resources to reconfirm or support any of the perfectly reasonable things we believe.
Thinkers in this tradition took the universe to revolve around humanity, and sought to gain knowledge of nature by finding parallels between us and the heavens, seeing reality as a symbolic work of art composed with us in mind.
We no longer expect there to be any special human significance to natural facts and we think knowledge will be gained by systematic and open-minded observations of nature rather than the sorts of analogies and patterns to which Sizzi appeals. However, the transition into the Modern era was not an easy one. The pattern-oriented ways of thinking characteristic of pre-Modern thought naturally appeal to meaning-hungry creatures like us.
Born in France in 1596, Descartes received a traditional Jesuit education, steeped in the classical ideas of Aristotle and his medieval interpreters. When he was later exposed to the newly emerging ways of studying nature, he had second thoughts about what he had learned in school. His Meditations begins with the confession that he had swallowed a “large number of falsehoods” as a child. “I realized that it was necessary to demolish everything completely and start again right from the foundations if I wanted to establish anything at all in the sciences that was stable and likely to last.”
Among all of his ideas, there is one that stands out to him at the top of the scale: his idea of God, an infinite and perfect being. The idea of perfection couldn’t possibly come from any less-than-perfect source, Descartes reasons, and he concludes that this idea must come from God himself, and must be innate, planted within us from the start.
The purpose of our sensations and related powers of imagination, Descartes ultimately concludes, is not to show our souls the true natures of things as they are in themselves (that job is reserved for the intellect); rather, sensations serve the interests of the body and soul taken together. Sensations like hunger, pain, scent, and color help to ensure our bodily survival, which is itself something that a benevolent God could, of course, have wanted to protect. We can avoid being misled by our sensations if we keep in mind that they are not designed to show the true nature of things; rather, their deliverances need to be checked against and interpreted in the light of our clear and distinct ideas. We can separate dreams from walking life by observing the consistency and coherence of what we really experience, reassured by the thought that a benevolent God would not have left us trapped in a lifelong dream. Knowledge is possible when we coordinate our mental powers carefully, subjecting our confused sensations to the discipline of our innate rationality.
Locke worked on a theory of knowledge to rival Descartes’s, spending 20 years developing his main work, the Essay Concerning Human Understanding. The central goal of the Essay is to search out the bounds between opinion and knowledge. Locke was convinced that he could figure out the limits of what is humanly knowable by using what he called the “historical plain method” to study the natural operations of the human mind. Beyond the limits of what could be known, Locke argued, human beings could certainly have faith or opinion, but they should neither claim certainty, nor attack those who differ in matters of opinion or faith (the promotion of tolerance was a large part of Locke’s agenda in figuring out the limits of knowledge).
Knowledge has its limits, however, even when we take the greatest care to define our terms precisely. Locke defines knowledge itself as “the perception of the connection and agreement, or disagreement and repugnancy, of any of our ideas.” There are various ways in which ideas can be seen to agree to disagree: Locke calls these the “degrees” of knowledge.
The clearest degree of knowledge is intuitive knowledge, and this is what we have when we immediately grasp the agreement or disagreement of some ideas. A slightly more difficult kind of knowledge is demonstrative knowledge, in which the mind sees an agreement or disagreement among its ideas but only with the help of some chain of connecting ideas: our knowledge that the internal angles of a triangles add up to 2 right angles is demonstrative knowledge, because it runs through a series of stages.
The last grade of knowledge is what Locke calls sensitive knowledge. Sensitive knowledge differs from the other kinds in being concerned not with general truths or relations among ideas, but with the existence of a particular objects that we experience. According to Locke, you have sensitive knowledge of the existence of the things you are sensing: for example, the clothes that you are now wearing.
Locke also puts a heavy emphasis on the adequacy of our knowledge for our practical purposes: if what seems to be real is real enough to be a reliable source of pleasure and pain, then you can be as certain that it exists as you need to be. For Locke, knowledge is above all a tool for the pursuit of happiness.
Knowledge is not our only guide. Locke argued that many of our actions are governed not by knowledge but by something weaker, namely judgment. Judgment doesn’t give us certainty, but it allows us to hold that a claim is probably true — and in many cases, the probability is high enough that we can treat it as practically certain. What we believe on the testimony of others is always a matter of judgment rather than knowledge.
As you wait for the announcement, do you know that your ticket has not won? Odds are 99.9% that it has lost, but most people say that despite the slim odds of winning, they don’t know that they have lost until the announcement is made. But if a 99.9% chance isn’t high enough for knowledge, how high do our chances need to be?
But the other key assumption in the analysis-of-knowledge project is more controversial. Are the building blocks of belief and truth really simpler than knowledge itself, and is knowledge really a compound built out on those factors?
Maybe not. In particular, it’s not obvious that believing is simpler and more basic than knowing. What if knowing is the fundamental idea, and believing is a spin-off from it?
According to Williamson, rather than trying to explain knowledge as a compound state formed by adding various factors to belief, we should explain believing in terms of knowing: “Believing p is, roughly, treating p as if one knew p.” In his view, knowing is a state of mind that essentially involves being right; believing is a state of mind that ideally aims at being right, while perhaps falling short of that target.
The world is popularly used for stage magic acts in which a magician performs an impossible-seeming trick of reading another person’s thoughts. As psychologists use the term, it applies to something that we do a hundred times a day with no special fanfare. Mindreading is the attribution of “hidden” or underlying mental states — wanting, fearing, thinking, knowing, hoping, and the rest — to another person. when you see someone reach towards something, you do not simply have the impression that an arm is extending in space; you see the person as reaching for the salt, wanting something, and aiming to get it. Without a capacity for mindreading, we’d be stuck looking at surface patterns of moving limbs and facial features; mindreading gives us access to deeper states within a person.
It’s not surprising that mindreading comes to have its own specialized area in the adult brain: although we can do it effortlessly, mindreading involves some complex calculations.