Knowledge summary

Knowledge, so the saying goes, is power. But in the current climate, knowledge can also be extremely confusing. Every day, we’re inundated with information. Some of it is authentic. Some of it is misleading. And much of it is downright false. We circulate select knowledge within social and political bubbles, but rarely tap into the knowledge that exists outside these bubbles.

Perhaps it’s time we got more critical about what we know – or what we think we know. And epistemology offers the perfect starting point for critiquing all things knowledge. This philosophical field studies the concept of knowledge – how it’s generated, circulated, and absorbed. These blinks outline key concepts in the field.

In these blinks, you’ll learn

• the intricate ways in which belief connects to knowledge;
• the secrets of mind reading; and
• why we may or may not know that Mount Everest is the world’s tallest mountain.

Let’s leave Protagoras’s theories behind and assume that we can only know things that are true. Furthermore, let’s accept that, according to the prevailing philosophy, truth is objective and exists outside of us. Think of truth as an electrical outlet: if we can plug into that outlet, we access knowledge.

But can we plug into that outlet? A skeptic might argue no, not really.

This is the key message: According to skeptics, we might not know what we think we know.

Here’s a thought exercise: Are you wearing shoes right now? You might think you know the answer. But how do you know that you know? How, for example, can you be sure you’re not in a dream? You might feel this line of thinking ties your brain in needless knots. But that’s how skeptics approach knowledge. And, in this approach, even the most apparently straightforward fact becomes problematic.

Skeptical philosophy originated in ancient Greece, where there were two key schools of skepticism. The Academic school believed knowledge was impossible. The Pyrrhonian school simply avoided reaching any conclusions. Both traditions hark back to the earlier Stoic conception of knowledge. Stoics distinguished between impression, or what you perceive, and judgment, which is your decision whether or not to accept what you perceive. A friend walking toward you creates an impression. But is the impression correct? Could the person be someone who simply looks like your friend? The Stoics believed in accepting only correct impressions. That means waiting until your friend is close enough for you to judge whether it's really her.

The Academic skeptics agreed with this approach, but they rejected the idea that any impression could ever be indisputably correct. You could be hallucinating. Your friend could have an identical twin. You never have any way of knowing even the things that you believe you know.

The Pyrrhonians took skepticism even further. To them, the Academic skeptics’ assertion that knowledge can never be indisputably proven was, in itself, a form of knowledge. They refused to be drawn on the question of whether or not humans could ever attain knowledge. In fact, they refused to be drawn on the question of anything. They considered it a virtue to keep an open mind on every topic. A well-known Pyrrhonian skeptic, Sextus Empiricus, even proposed handy catchphrases fellow skeptics could use to prevent them from ever leaving a state of doubt, like “I determine nothing” and “Perhaps it is and perhaps it is not.”

Were we to follow in the footsteps of the Academic skeptics, our discussion of knowledge would end here. The Pyrrhonian skeptics, meanwhile, would say the discussion should never end. Luckily, other influential thinkers come at the topic quite differently.

Remember how the skeptics posited that we can never truly know anything? Well, not everyone agreed. On the opposing team, there are two heavyweight thinkers: Rene Descartes and John Locke.

Descartes and Locke were both key figures in the early modern philosophy of the seventeenth century. Both made influential contributions to epistemological thought, refuting the skeptics’ view that knowledge couldn’t be accessed. But that didn’t mean they agreed on everything.

Here’s the key message: Descartes’ rationalism and Locke’s empiricism advanced two new understandings of knowledge.

Unlike the skeptics, Descartes was a rationalist who believed humans could apprehend fundamental truths. The most fundamental of these, as set out in his 1641 treatise Meditations, is this: one can be completely certain about the truth of his own existence. Furthermore, Descartes was certain of the truth of God’s existence. He reasoned that the idea of God was the idea of perfection itself. And the idea of perfection couldn’t come from an imperfect – or, in other words, human – source.

According to Descartes, we know that the self exists and that God exists. In fact, Descartes believed that we apprehend the existence of these things – along with other abstract, rational concepts like numbers, geometry, and truth itself – innately. In other words, humans are born with a set of in-built truths. 

Locke was on board with some of Descartes’ work, but he didn’t share Descartes’ high opinion of humankind. After all, do we really behave as though we’re innately supplied with rational ideas? Babies, for example, didn’t strike Locke as beings endowed with innate rational principles. 

Locke thought we came by ideas through sensation. As infants, we’re exposed to all kinds of sensations, which, through repetition, we slowly organize into patterns and understandings. From these early sensations we develop powers of reflection, as we learn to observe our own mental workings. Sensation and reflection, according to Locke’s theory of empiricism, make up the fundamentals of human knowledge. 

But, as Locke himself acknowledged, we’re each exposed to a unique set of sensations and reflections. By Locke’s logic, Descartes’ idea that we all apprehend concepts like love or justice in the same way just didn’t hold up.

Why not follow Locke’s train of thought a little further? If we accept that, contrary to Descartes’s view, knowledge isn’t innate, then the conditions through which we come to know something suddenly get more complicated. 

Centuries later, in the 1960s, a so-called classical analysis of knowledge was proposed to better explain these conditions. The elements of this analysis claim that a subject can only know a proposition when the proposition is factual, when the subject believes in the proposition, and when the subject is justified in her belief.

This is the key message: Knowledge and belief have a crucial, yet slippery, relationship.

To illustrate, here’s one of Bertrand Russell’s famous philosophical puzzles:

A man is rushing to catch his train. Does he have time? He glances at the station clock. It says 1:17 p.m. It is his true, justified belief that the time is 1:17; therefore, he knows the time. But what if the clock is broken and it’s actually 1:33 p.m.? Can the man still “know” it’s 1:17? Well, no. He’s operating on a false belief.

But there’s a problem with this classical analysis, which suggests that a false belief can’t lead to knowledge. Imagine a detective gathering evidence to show that a man killed his wife. The detective has the gun, and the man’s fingerprints, not to mention several eyewitness accounts. The detective believes, correctly, that the man killed his wife. But one of the eyewitnesses is lying. Is the detective’s knowledge now invalid because it was predicated on a false belief? According to philosopher Edmund Gettier, it’s not. This example proves that you can have knowledge, even if some of the beliefs supporting that knowledge are false.

As Gettier’s example shows, the classical analysis of knowledge isn’t watertight. But could it be made so? Alvin Goldman proposed the theory of causal knowledge, which sidesteps “true” or “false” belief to suggest that belief in a fact must have a causal connection to that fact. If you see a house on fire, for example, your experiential knowledge of what a fire is and how it behaves will create a causal connection to the fire you’re now witnessing. But this, too, is fallible. To channel the skeptics, we could ask: What if what you thought was a house on fire was actually a very convincing hologram?

Since the 1960s, epistemologists have struggled to analyze the relationship between belief and knowledge. Many doubt the relationship is really analyzable at all. But while there might be no exact formula through which to explain it, delving into this relationship continues to produce more insights into how we might know what we know.

As we learned in the last blink, after Gettier problematized the classical analysis that knowledge rests on justified true belief, Alvin Goldman proposed the causal theory of knowledge. In fact, Goldman’s theory belongs to a broader category of epistemological theory called externalism.

To understand externalism, let’s look at Mount Everest – which you probably know as the world’s tallest mountain. But how do you know this? Unless you received this fact when you were also, say, having your first kiss, you won’t remember exactly how you learned it. You picked it up from a number of sources, and you feel it’s right. According to externalists, you know that Everest is the world’s tallest mountain.

Here’s the key message: Epistemology calls even basic facts into question.

Here’s a problem with the Everest example. Externalists argue that to know this is true, it’s sufficient to have a relationship to the fact that it’s the world’s tallest mountain. But plenty of people have a relationship to the “fact” that Sydney is the capital of Australia – when, really, it’s Canberra. It’s easy to have a false relationship to a fact.

Now, internalists take a different approach. They’re of the “seeing is believing” school. To know something, you must have supporting evidence. Have you measured Everest against all the other mountains in the world? Is there a formula you can use to determine its superior height? No? Then you really don’t know that Everest is the world’s tallest mountain; you’re simply giving your belief the status of knowledge.

In short, externalists believe we can know something without clear-cut evidence, while internalists believe we can’t. Which isn’t to say that internalists believe we shouldn’t think of Everest as the world’s tallest mountain. For all intents and purposes, we should! We should simply, out of philosophical interest, question whether this is something we can really know.

That doesn’t mean that internalists think you can never know anything. In fact, they place great significance on systematic first-person thinking. They believe we can know lots of things, through our senses, our powers of deduction, and our powers of reflection. By thinking carefully through our movements – and perhaps checking the grocery store receipt – we can know what we had for dinner last night. 

Externalists believe in the power of first-person thinking as well, though they’re happy to accept the results of automatic thinking as knowledge – meaning that it’s enough to know automatically that pi is roughly equal to 3.14 without understanding the math behind the number. 

Both internalist and externalist schools of thought see first-person thought – though different modes of it – as a reliable source of knowledge. But what happens when we bring another perspective into the equation? 

There’s no denying that much of what we know about our world is secondhand knowledge, learned through the accounts of others. We know about life in ancient Rome because we can read about it; we know about events unfolding on the other side of the globe because we see them in the news.

But can secondhand testimony count as a form of knowledge?

The key message here is: Testimony is a form of knowledge that divides epistemologists.

Remember John Locke? His view was that we gain knowledge through perception. Therefore, he thought we could never truly know something we learned from someone else’s account. Locke’s position is pretty hard-core. In fact, by Locke’s own logic, we can assume that a philosopher named John Locke existed in the seventeenth century – but we can’t know for sure. 

Other philosophers, known as reductionists, have tried to strike a compromise. They believe we possess critical faculties, like inference, memory, and – Locke’s favorite – perception. These faculties enable us to assess the reliability of testimony, and the knowledge it contains. In this way of thinking, perception is still key – but we can also confidently say that, for example, Mars exists without needing to visit it ourselves.

Some philosophers, on the other hand, take up the opposite position from Locke. They argue that testimony is itself a form of knowledge, and that we can access it without depending on other forms of knowledge, like perception. There’s one condition, though: The person who’s giving the testimony – the informant – has to be telling the truth.

Interestingly, in this school of thought, the informant doesn’t have to believe in the knowledge he imparts in order to be truthful. We can receive true knowledge from a less-than-perfect source, like a creationist teacher who is nevertheless obliged to teach the theory of evolution to his students. 

An imperfect source might also collaborate with others. For example, you might be at a dinner party where the topic of top-selling albums comes up. Your partner might have a hunch that Michael Jackson’s Thriller is the best-selling album of all time, then confirm this by checking online. This wouldn’t satisfy Locke, who would argue that we can only probably say Thriller is the world’s best-selling album. But unless your dining partners are Lockeans or reductionists, that online check should settle any dinner-table debate.

Some epistemologists consider the question of whether secondhand testimony counts as knowledge, or whether we can ever know something when our knowledge is based on a false belief. But there’s one school of thought, contextualism, that cuts through these questions. As the name suggests, their position is this: It all comes down to context.

This is the key message: Knowledge depends on context.

Imagine a father takes his daughters to the zoo. He points at a horse-like animal with black-and-white stripes and says, “Look, girls, a zebra!” How does he know this zebra isn’t a donkey painted black and white? Well, according to what’s called the relevant alternatives theory, he knows because in the context of a well-maintained zoo, the idea that the creature is a painted donkey simply isn’t a relevant alternative to the idea that it’s a zebra. In a dodgy sideshow attraction, the story might be different. Relevant alternatives are context-dependent.

Building on the relevant alternatives theory comes the idea of contextualism, which suggests that the criteria we have for knowledge are context-dependent.

These criteria are applied differently in different situations. A six-foot-four basketball player might describe himself as tall in his online dating profile. He’s applying broad criteria here: generally speaking, 6’4” is tall. A sports commentator, talking about the same basketball player, might describe him as “not very tall.” The commentator wouldn’t necessarily be wrong. Not according to the stricter criterion of height among pro basketball players.

Contextualism even creates room for the average person and the skeptic to coexist. An ordinary person who is barefoot can say, “I know I’m not wearing shoes.” A skeptic who is barefoot might ask, “How can I know if I am wearing shoes or not? I might just be experiencing a vivid hallucination that I am barefoot right now.” The contextualist would argue that both the average person and the skeptic are right – they’re just applying different criteria to the very concept of knowing.

But even a contextualist can’t please everybody. Some thinkers believe that knowledge is immutable – that truth doesn’t shift from person to person or between situations. For these thinkers, contextualism is a pretty radical idea. And the next idea we explore might be even more radical.

There’s another method for attaining knowledge that we haven’t discussed yet. And it’s one you use all the time, without even being aware that you’re using it. It’s intuition.

Think about it. If your friend Sam tells you, “I’m in line for a new position at work,” you might report that news by saying, “Sam knows he got the job.” Then again, you might say, “Sam thinks he got the job.” You don’t have to ponder which verb to choose. We don’t need to do that because, subconsciously, we can often intuit what other people know, what they’re unsure about, and what they don’t know.

The key message is: Humans can intuit others’ knowledge.

Through our intuition, we achieve something pretty remarkable: mind reading. We don’t do this in the Las Vegas magician sense; we can’t read people’s thoughts word for word. Epistemologically, mind reading refers to our ability to intuit others’ mental states. We’re able to guess what others know by making subconscious inferences.

In this respect, we’re like many other animals. Chimpanzees use mind reading to assess whether rival chimps have discovered their food stash. But while chimps can keep track of whether their fellow chimps have knowledge or lack it, only humans can manipulate a perceived lack of knowledge. We do this through, for example, practical jokes. When we offer a friend a can of peanuts with a rubber snake inside, we are intentionally playing on her lack of knowledge of what that can really contains. 

Even though our ability to intuit knowledge is impressive, it has its limits. We can track more than one mental state at a time. We can intuit, for example, that Rhonda thinks that John knows about the affair she’s having. We can even intuit that John believes that Rhonda thinks that John knows about her affair. But we tend to max out when we’re asked to keep track of more than five mental states.

We’re also egocentric. It’s hard to factor what we know out of the equation when intuiting what someone else knows. It’s been shown that when two people are stock-trading, and one person is given insider information, the more informed participant has difficulty predicting how his opponent will trade. The person with the insider knowledge struggles to subtract that knowledge from what he knows of his opponent’s knowledge.

Despite its limitations, however, our intuition shows just how knowledge connects us, and how we connect through knowledge. Epistemologists still grapple with the idea of what knowledge is. But there’s no denying that knowledge is integral to ourselves, our relationships, and our understanding of our world.