Introduction

Most people have spent some time wondering about whether they truly know what they (seemingly) know. You may have asked yourself, “how do I know that I’m not in a simulation? Or maybe you asked, “how do I know that other people are conscious and not just thoughtless robots?” You may have also doubted your beliefs about smaller (yet still important) matters such as, “did I leave my keys in the car” or “can I know that my wife truly loves me?” These questions are examples of skeptical worries, which is a major area of focus in epistemology.

In short, skepticism is the view that there is some fact (or a group of facts) that we do not know. Every reasonable person would hold that there are some facts that we cannot know, for example, I believe that it would be impossible to truly know whether there are an even or an odd number of pieces of sand in the universe. So, we are all skeptics about some things. As you would probably expect, people disagree about what they can know and what they can’t know. For example, an agnostic may claim that you can never really know whether a religious belief is true or false while a priest would likely disagree. It is thus important for us to distinguish different types of skepticism.

In this chapter, I will cover various common forms of skepticism that epistemologists discuss. This includes global, local, and Cartesian skepticism as well as the problem of induction. I will furthermore explain why different epistemologists endorse and reject skeptical these skeptical stances. Finally, I will cover fallibilism and the Moorean response to global skepticism. By the end of this chapter students should be able to:

• Explain the differences between global and local skepticism
• Students should be able to explain why knowledge of the external world seems harder to attain than knowledge of one’s own mind
• Students should be able to explain Descartes’ cogito argument
• Students should be able to explain the problem of induction
• Students should be able to explain fallibilism and how it can respond to skepticism

Global Skepticism

Global skeptics believe that it is impossible to know anything. A global skeptic would say that, despite what you think, you do not know that you are awake, you don’t know that 2 + 2 = 4, you don’t know that your mom loves you, and you don’t know that your best friend isn’t secretly a robot. Most people believe that you can genuinely know some facts, so most people are not global skeptics. Despite the unpopularity of this view, it still presents a difficult epistemological challenge.

René Descartes was a famous French philosopher and mathematician who wrote an incredibly influential text called The Meditations on First Philosophy. This text is perhaps the most famous text on skepticism and is an outstanding work of epistemology. In The Meditations Descartes attempted to doubt everything that he believed and then tried to prove that he did know some incredibly important facts (e.g., the fact that he was awake as well as theological and mathematical facts). There are many aspects of the text that are flawed; however, his philosophical methodology was brilliantly well structured which is why people are still studying this text hundreds of years after it was published.

Descartes engaged in methodological doubt to set up the problem of global skepticism. This is how his process of methodological doubt works: you first consider some fundamental belief that you have, and you then attempt to construct a skeptical scenario in which you would still have that belief even if it was wrong.[1] If there is such a scenario, then (according to Descartes) you don’t really know that belief since you could be wrong. In other words, if (for all you know) you could be wrong about a certain belief, then you can’t claim that you truly know that belief. Thus, at least for the sake of this book, Descartes required that somebody must be absolutely certain of their belief to achieve knowledge. One fundamental belief that Descartes doubted throughout the book was the belief that his senses provide him with accurate information about the world. For example, if Descartes saw a table, then he automatically believed that the table existed in the real world (this is a normal reaction of course). However, Descartes noted in the first and second meditations (or chapters) that it is rather easy to construct a skeptical scenario in which he would hold the same belief (the belief that the table exists in the real world) when it in fact isn’t. After all, such skeptical scenarios are certainly not unheard of. Descartes points out in his first meditation that we all have dreams and we all (usually) believe that our dreams are real while we are dreaming. It thus follows that he couldn’t completely rule out the possibility that he was in fact dreaming. Thus, Descartes realized that he didn’t have complete certainty that the table that the saw existed in the real world. He thus concluded that he did not yet know that what he saw was an accurate picture of the world.

Remember, global skeptics believe that you cannot know anything at all. Thus, Descartes couldn’t just doubt his beliefs that stem from his senses if he wanted to present global skepticism. He also needed to (and did) consider beliefs of more conceptual concepts, such as beliefs in mathematics. In philosophy there is often a distinction made between beliefs that are a priori from beliefs that are a posteriori. It is hard to come up with a perfect definition for these concepts; however, to put it simply, beliefs that are a priori can be known without the aid of one’s senses while beliefs that are a posteriori can only be known with the aid of one’s senses. Consider the following example:

Robot Bob: Dan is a mad computer scientist who is attempting to develop artificial beings that are truly intelligent (meaning that they are aware of their own existence and can control their own thoughts). Dan, being the creator of these beings, decides what knowledge will be preloaded into the AI as well as how the AI can sense. For example, one AI he created was preloaded with knowledge about astronomy and given access to a camera that connects to a telescope. The AI could then make new discoveries about astronomy since it had the necessary background information and an ability to see the stars in real time. Dan is working on a superintelligent AI, Robot Bob, who is smarter than a thousand Einstein’s; however, before booting him up for the first time, Dan must decide what information (if any) to preload into Robot Bob and what Robot Bob can sense. Out of curiosity Dan decides to boot up Robot Bob without preloading any knowledge into him and without giving him the ability to sense anything. Thus, Robot Bob’s existence is the equivalent of the mind of a thousand Einstein’s in a void.

The Robot Bob case is a bit odd, but it provides us with a pretty good method of distinguishing the a priori from the a posteriori. If Robot Bob (without any previous knowledge or the ability to sense) can conceivably learn some fact, then the belief of that fact is a priori. But if Robot Bob could not learn that fact then it is a posteriori. What facts could Robot Bob not learn? Well, Robot Bob lacks any ability to sense so he couldn’t learn what the color of the table is in Dan’s laboratory. However, Robot Bob could perhaps learn that 2 + 2 = 4 since that is a truth which does not require observation to learn. It only requires intellect.

Moving back to Descartes, we have seen so far that Descartes gave us reason to doubt a posteriori knowledge (since our senses would not be an accurate description of the world if we were dreaming). But—since Descartes was considering global skepticism—he also had to doubt a priori beliefs. Since we are thinking of possible scenarios in which we would still have our beliefs even if the belief was false, we should consider whether the scenario that we have considered already also leads to doubt about a priori beliefs. So, is it possible that you could dream that mathematical facts are different than they are? Could we merely believe that 2 + 2 = 4 since we are dreaming? If we were dreaming then woke up, could we realize that 2 + 2 = 5? Descartes claimed that this is an impossibility in his first meditation. So, (according to Descartes) any sort of mathematical fact which is true in the real world would also have to be true in a dream.[2] Thus, Descartes needed to think of a different scenario if he was going to present global skepticism as a plausible view.

The ultimate skeptical scenario that Descartes landed on in his first meditation was a scenario in which he believed everything that he believed but only because a powerful evil demon was deceiving him. According to Descartes, on first glance, a person in this scenario could be mistaken about all their beliefs. This would include beliefs regarding a priori propositions (such as ‘2 + 2 = 4’). Thus, since Descartes (initially) contended that this evil demon scenario could extend skeptical concerns to all branches of belief (both a priori and a posteriori), this was the scenario that Descartes used to showcase global skepticism.

In response to global skepticism, Descartes made the famous and brilliant cogito argument in his second meditation which is widely held to be a knockdown response to global skepticism. Before I explain what the argument is, I should explicitly state that global skepticism would be proven false if there was just one belief that somebody could not be mistaken about (which is exactly what the cogito argument claims). The argument can be summed up by the famous phrase “I think, therefore I am.” Essentially, Descartes claim was that it would be impossible for someone to think “I think, therefore I am’ and be mistaken, since something cannot think if it doesn’t exist. Thus, Descartes claimed that there is no possible skeptical scenario in which that statement could be false.

It is worth noting that in the cogito argument, Descartes used the words ‘I’ and ‘am’ in an incredibly weak fashion. So, ‘I think, therefore I am’ should not be translated to ‘René Descartes—French philosopher and mathematician—thinks, therefore René Descartes physically exists’. After all, if the cogito argument translated to this, then a person in an evil demon scenario could believe this and be wrong (perhaps the thinker is actually an ethereal Albert Einstein being deceived to think that he is Descartes physically existing). Instead, ‘I’ should be read as ‘the thing that is thinking’ (which Descartes explicitly states in his third meditation) and ‘am’ should be read as ‘exists in an abstract or physical manner’. This reading of the cogito argument withstands the evil demon scenario.

I have explained why the cogito argument disproves global skepticism; however, you may notice that Descartes really has not proven much (so far at least). Sure, I can confidently say that I know that I, a thinking thing, exists; however, if that’s all I know, then I am still stuck in a skeptical nightmare. Descartes recognized that the cogito argument is severely limited in scope and thus tried to build up to more substantive knowledge. Essentially, Descartes believed that the knowledge gained from the cogito argument acted as the foundation for the rest of his knowledge, and that he could build up his knowledge from that foundation with absolute certainty.[3] Descartes unfortunately failed to prove much else in his remaining meditations. To give a brief overview, he attempted to prove that God existed in his third meditation, and he essentially wanted to show throughout the remaining meditations that we could be confident in a wide variety of other facts due to God’s perfect existence. It is clear upon reading his arguments for the existence of God that he did not really doubt all of his preexisting beliefs since you can see them creep up in his arguments.

I have shown that Descartes disproved global skepticism yet was unable to show that he knew much beyond the knowledge in the cogito argument. As I said earlier, if you only knew that you existed then you would be stuck in a skeptical nightmare. Thus, it is worth denoting a term for the skeptical stance that you can only know the contents of your thoughts and that you exist, we can call this view external world skepticism (some people also refer to this as Cartesian skepticism).[4] Beyond the evil demon scenario, a possible skeptical scenario that reinforces external world skepticism is what we would refer to as a brain-in-a-vat scenario. Essentially, we can imagine a situation in which an evil scientist has taken a brain and put it in some high-tech rig which allows him to control the contents of the brains phenomenal experience (this is similar to the plot of The Matrix). If this was the case, then the brain could know what it was thinking, it could know that it existed, yet it would be unable to know anything beyond that.

Local Skepticism

Local skeptics believe that there are some truths that cannot be known and other truths that can be known. It follows from this definition that external world skeptics (or Cartesian skeptics) are in fact local skeptics since they believe that they can know a variety of truths (what they can access in their minds); however, they do not believe that you can know any sort of mind external truth. Although that label is technically accurate, philosophers generally use the term ‘local skepticism’ to refer to narrower domains of facts. In this section I will cover a few of these narrow skeptical domains.

The Problem of Induction

The first form of skepticism that I will talk about in this chapter is the problem of induction which is a problem attributed to the brilliant Scottish philosopher David Hume (1739).[1] The problem of induction refers to an inability to epistemically justify induction, which is a very common form of reasoning. To simplify, induction is a form of reasoning in which a person makes some observation regarding a domain of something they do know, and then use that observation to make a prediction regarding some domain they do not know.[2] It is genuinely used as a way to make a prediction about something in the future based off of something that happened in the past. For example, if your doctor says, “you will recover fast from this surgery, every patient who has ever had it did,” then they are observing the fact that all patients who had that surgery in the past recovered fast, and then making a prediction regarding how fast you will recover in the future. Although induction generally refers to this past-to-future prediction, it doesn’t have to. For example, somebody may say, “all species of birds ever observed by science have had feathers; thus, this prehistoric bird probably had feathers.” In this example the reasoner makes an observation regarding what has happened in the past (the fact that all species observed by science have had feathers) and then makes some prediction about another thing that happened in the past (the prehistoric bird having feathers).

Induction is a very common form of reasoning that is used in nearly every area of study or thought. It is a crucial component of the scientific method since most of science involves making observations and then making a prediction based upon those observations. For example, we believe that gravity is a universal constant since the law of universal gravitation holds everywhere that we have observed. Induction is also used in more casual domains. For example, my students believe that I will arrive to class on time since I have always arrived on time in the past.

We often talk about justifying specific beliefs in epistemology, but it is also important to justify specific forms of reasoning. For example, if I decided to flip a coin in attempt to determine whether some specific statement was true, then I would not be epistemically justified in believing that statement. Thus, the coin-flipping method of reasoning is not a justified form of reasoning. Induction is a very common form of reasoning; however, we still need to justify induction as a form of reasoning before we can justify any specific belief using induction. So, how do we know that induction is a justifiable form of inference? The obvious answer is that we have used it in the past before and it has worked. Although this answer seems obvious, it is problematic since it is in fact circular.

An argument is circular if it uses the conclusion of the argument as a reason to believe the argument. For example, if I said, “my grandmother is honest, she told me she is” then I probably wouldn’t be very convincing because you need to believe that my grandmother is honest in order to give any credence to the fact that she told me she is. Thus, I am using the conclusion of the argument (the claim that my grandmother is honest) to justify the conclusion (the claim that my grandmother is honest). This is obviously a mistake since I am not actually providing any reason to believe the conclusion since I need to assert the conclusion for you to believe it. It follows that a circular argument is not justified.

How was our justification for induction circular? Well, we justified induction by stating that we have observed it working before and we thus assume that inductive inference works. However, inductive inference itself is the type of inference where somebody makes an observation and follows it up with a prediction based upon those observations. Thus, our justification is akin to saying that we know that we can justifiably make a prediction based upon past observations since we have made predictions based upon observations in the past and it worked. In other words, the obvious justification for induction relies on induction, which makes it circular and thus unjustified.

Induction is an intuitively justified form of reasoning; however, it seems like the obvious method of justification doesn’t work. Thus, it becomes unclear how we are supposed to get away from the problem of induction. There are no easy solutions that seem satisfactory. One potential solution which has been written about by Richard Feldman (2003: 137-9) is to say that induction is a form of reasoning that is foundational and inherently justified. Epistemologists who hold this position argue that there are certain forms of reasoning which do not need to be justified since they are just so basic. Thus, since induction does not need to be justified, it follows that there is no problem of induction. I do believe that this solution is our best bet; however, it does feel cheap in a sense. Many people feel that claiming that induction is foundational is being used as an easy way to dismiss the problem.

The Problem of Other Minds

The next problem that I will discuss is the problem of other minds which is a common form of skepticism which has been discussed by many philosophers such as René Descartes and David Chalmers.[3] The problem of other minds relates to an inability to prove that other people are conscious. Descartes showed with his cogito argument that a person can know with certainty that their mind is conscious; however, that person cannot know with certainty that other minds are conscious. It is possible (for all that I know) that I am in a simulation and everyone else in the simulation is an artificial intelligence or—to put it in video game terms—a non-playable character. Alternatively, it is possible that I live in the physical world; however, everyone I know are cleverly designed robots that merely walk, talk, look, and act like conscious beings.

It is clear that there is a discrepancy between the amount of certainty that I can have regarding my own consciousness and the amount of certainty that I can have regarding the consciousness of others. I take it as granted that we cannot know that other minds are conscious if we require certainty to attain knowledge. However, many epistemologists claim that we can know facts (such as the statement that other people are conscious) despite lacking complete certainty in those facts. Thus, many epistemologists will respond to the problem of other minds by saying, “I have very good reason to believe that other minds exist.” I’ll talk about this attitude in the next section.

Fallibilism

Fallibilists believe that somebody can achieve knowledge even if they are not absolutely certain of their belief. Or in other words, fallibilists believe that knowledge does not require infallible access to the truth. This stance is contrary to the standard of knowledge that Descartes held in his Meditations on First Philosophy. Descartes believed that one could not truly know that the physical world existed if they could not rule out the possibility that an evil demon was deceiving them. Of course, Descartes did not think that there was any reason to believe that an evil demon was deceiving him; however, the fact that this scenario was improbable did not matter to Descartes. The fallibilist would be comfortable disregarding this scenario due to the improbability of it. Thus, the fallibilist position is a rebuttal to global skepticism and external world skepticism.

It is important to note that fallibilists still believe that knowledge requires truth, belief, and justification/warrant. Thus, somebody cannot know a belief that is untrue (even if they belief it). The fallibilistic aspect attaches onto the believer’s reasoning. The fallibilist claims that a believer needs good but not perfect reason to justify/warrant their belief. If that justified/warranted belief is also true, then it is by definition knowledge. Thus, if I believe with good reason that I am not being deceived by an evil demon, and if I’m not, then I have achieved knowledge. I may not possess knowledge that I know that the evil demon scenario is false, but that does not mean that I do not know that the evil demon scenario is false.

Fallibilism can also help the epistemologist avoid certain locally skeptical problems. For example, fallibilism can be used as a response to the problem of other minds. If the fallibilist has good reason to believe that other people are conscious, and if they actually are, then the fallibilist knows that people have other minds. So, the question is, does the fallibilist have reason to believe that other people have minds? The answer seems to be yes given the fact that other people act just like you and have the same anatomy and biological wiring that you do. It would be very strange if you share these commonalities with other people yet differ in such a substantive way. Thus, assuming that other people are actually conscious, it seems like the fallibilist can know that fact. Of course, the fallibilist may not have perfect evidence, but they don’t need perfect evidence to achieve knowledge.

It is worth noting that fallibilism cannot necessarily solve all skeptical problems. Fallibilists still claim that somebody needs good reason to believe some fact to attain knowledge of that fact. Thus, if there is a skeptical problem that is characterized by a lack of reason to believe something, then fallibilism cannot offer an adequate response to that form of skepticism. You may recall that the problem of induction is characterized by a lack of reason to believe that induction is a justifiable form of reasoning (due to the alleged circularity of its justification). Thus, fallibilism cannot be a direct response to the problem of induction.

Fallibilists often argue that fallibilism is an intuitive stance which tracks how people genuinely talk about knowledge. To understand this, consider some facts that you are willing to say that you know. Here are a few statements that you may have thought of:

• The earth is round
• Epistemology is a topic in philosophy
• George Washington was the first president of the United States

These three propositions could intuitively be claimed to be known. However, it is clear upon reflection that we have not used infallible reasoning to come to these beliefs since there are potential skeptical scenarios that we cannot certainly rule out. For example, it could be the case that all world governments have covered up the truth of the Earth’s flat shape and that all evidence of the Earth being round has actually been fabricated. Additionally, it could be the case that all your philosophy professors and I have actually deceived you into believing that epistemology is a topic in philosophy. Perhaps it is actually a topic in botany, and we have fabricated evidence in textbooks to convince you that it is a topic in philosophy. Furthermore, there could also be a conspiracy to revise historical documentation by the illuminati to convince you that the first president of the United States was George Washington when it was in fact Weorge Gashington. Despite these possibilities, we are still pretty sure that we know these facts; thus, it seems that we intuitively have a fallibilistic conception of knowledge.

Beyond knowledge that we know, it is apparent that we consider knowledge to be fallibilistic when we look at scenarios from a third-personal lens. Consider this example:

Professor John and his Inductive Errors: John is a professor of physics at a prestigious university, and he has conducted numerous experiments that led to the discovery of groundbreaking facts about the universe. John has always shown a genius-level acuity for scientific reasoning, and he has a deep understanding of when it is appropriate to accept a hypothesis and when it is not. John has published twenty essays which detail the results of these experiments. However, unbeknownst to John, he made an error during one of these experiments and thus came to the wrong conclusion in his essay. Despite that setback, the other nineteen experiments were conducted perfectly, and he came to the right conclusion. Does John know those nineteen true hypotheses that he accepted?

I believe that the intuitive answer to this question is yes, John does know those nineteen hypotheses are correct. Despite this, John sometimes makes mistakes. Thus, it seems to be intuitive (from a third-personal point of view) that somebody can achieve knowledge even with fallibilistic reasoning. After all, everybody makes mistakes, even the most genius scientists and mathematicians make mistakes. We often talk about knowledge from a third-person perspective and thus it seems like following our intuitions can help us discover when it is appropriate to state that somebody ‘knows’ some fact and when it is inappropriate.

Despite the fact that fallibilism seems intuitive, fallibilism entails some stances that naturally seem unintuitive. For example, fallibilism notably entails that the KK Principle is false. The KK Principle states that if somebody knows a certain fact, then they must be able to know that they know it. This may be a bit confusing, but we need to make a separation from knowledge of some initial fact and knowledge of one’s knowledge. For example, imagine that Suzie knows that the Earth is round, and that Paul knows that Suzie knows that the Earth is round. In the previous sentence the statement “Suzie knows the Earth is round,” is the initially known fact and the statement “Paul knows that Suzie knows that the Earth is round” is a different fact. Many epistemologists believe that it is intuitive to state that if somebody knows a fact X, then she must be able to know that she knows X. Thus, if Suzie knows that the Earth is round, then Suzie must be able to know that she knows that the Earth is round. Afterall, it seems very unintuitive for somebody to say, “I know that the Earth is round but I’m not sure if I know it.”

It is important to note that many epistemologists have conflicting intuitions regarding the KK Principle. Some epistemologists simply don’t understand the appeal of the principle and think that it is unintuitive. Furthermore, some epistemologists think that upholding the principle entails stances that are more unintuitive than rejecting the KK Principle. For example, many epistemologists believe that fallibilism is an intuitive stance and thus are willing to reject the KK Principle. Thus, this argument has (to some extent) come down to a battle between intuitions which seems to be rather problematic for the epistemologist.

Final Thoughts

Skepticism is perhaps the most common area of discussion in academic epistemology. After all, the worry that we do not know what we think we know seems universal. That is why we watch movies such as The Matrix and The Truman Show. Thus, it seems like epistemologists and regular people have many of the same anxieties. Unfortunately, epistemologists cannot agree with each other and thus it seems like epistemology is probably not a topic which should be studied to help settle anxieties. Despite this depressing point of view, epistemologists have begun to gain deeper insights into what people think the requirements for knowledge are, which is a critical task that philosophers should (and likely will) engage in for another two thousand years or so.

What should philosophers work on next? It seems to me that the two biggest points of contemporary contention that I talked about in this chapter are the problem of induction and fallibilism. It seems clear to me that we need to find a way to justify induction if we want to be able to confidently say, “we know a lot of stuff,” since induction is one of (if not the) most common and important forms of reasoning that humans utilize. Fallibilism is important since adopting fallibilism would help us defeat external world skepticism once and for all.

Comprehension Questions

Reading Suggestions

Primary Sources

Chalmers, David, The Conscious Mind: In Search of a Fundamental Theory

Descartes, Rene, Meditations on First Philosophy

Hume, David, A Treatise on Human Nature, book 1, part iii, section 6

Secondary Sources

Feldman, Richard, Epistemology, chapters six and seven

Great Works of Fiction

Dick, Philip K., Do Androids Dream of Electric Sheep?

Vonnegut, Kurt, Slaughterhouse-Five