PHILOSOPHY – Epistemology: The Problem of Skepticism [HD]


[intro music] My name is Jennifer Nagel. I teach philosophy at the University of Toronto, and today, I want to talk to you about the problem of skepticism. What do you know for sure? Consider the fact that you are watching a video, on your computer, right now Is this something you “know?” Before you say yes, consider the following question: do you think it is possible for someone to dream that they’re watching a video online, when in fact, they’re asleep in bed, with their computer turned off. Can you prove that you are now awake and not dreaming? If not, do you know that you are watching a real video as opposed to dreaming one up? If you start feeling inclined to doubt that you have knowledge, you’re feeling the attraction of skepticism. Our word, skepticism, comes from ancient Greece, the home of not one, but two great skeptical traditions, academic skepticism, and Pyrrhonian skepticism. Academic skeptics argued that sensory impressions, which are often taken to be the foundation of knowledge about the world, don’t actually enable you to know anything. Do you have the impression that the voice you’re hearing now, is the voice of the same person who narrated the first video in this series? I might have an identical twin. You might be mis-remembering, dreaming, or in some other way making a mistake. Because impressions can be misleading, you can’t know that the same person is narrating both videos. The academics used arguments like that one to support their general conclusion that knowledge of the world is impossible for humans. Pyrrhonian skeptics went one step further. Their mission was just to keep on inquiring, and doubting everything without reaching any conclusions at all. Where the academic skeptics argued that knowledge was impossible, the Pyrronian skeptics worked to suspend judgment even on that point, keeping all questions open. Some skeptical arguements have been known since antiquity and used in both eastern, and western philosophy. Most famously, the dreaming argument. If what you are now experiencing is just a dream, then it’s not clear that you know anything about your immediate environment Or even about yourself. The ancient Chinese philosopher Xiang Xiu [Jwang Ju], reported having dreamed that he was a butterfly, and worried later that he did not know whether he was then, a man dreaming he was a butterfly, or whether, he might now be a butterfly, dreaming he was a man. You might think that there are some facts you could know whether or not you are dreaming. The 17th century philosopher, Rene Descartes, suggested that even if you are dreaming, you should still be able to know that a square has four sides, or that 2+3=5. But Descartes found a way to raise skepticism about those facts, too. He noted that it feels natural to us to make those simple mathematical judgments, but pointed that we could ask whether what feels natural to us really has to be true. Where does our nature come from anyway? Decartes also developed a powerful skeptical scenario, designed to make you doubt absolutely everything, including your grasp of abstract fact. Imagine that there is an evil genius of utmost power and cunning, devoted to deceiving you. The evil genius controls all your sensory impressions and all your instincts, about math, and geometry, and so on. Making false things seem true to you. The challenge of skepticism, Descartes argues, is the challenge of proving that you are not, right now, in the hands of such a demon. In the next video, we’ll look at Descartes’ own way of answering that challenge. Meanwhile, various other powerful skeptical arguments have emerged since Descartes’ time. The 18th century philosopher David Hume, had some especially good ones covered in detail in two separate Wi-Phi videos. Moving to the present day, we have a new version of Descartes’ evil genius argument. Imagine a brain kept alive in a vat, and connected to a supercomputer that delivers sensory signals to simulate the experience of a coherent reality. The computer also picks up the brain’s outgoing motor signals and adjusts its inputs accordingly. When the brain sends out motor signals to raise a hand and touch something, the computer delivers coordinated visual and tactile input of seeing the hand and feeling what it touches. If the computer program is good enough, and let’s assume that it is, the brain-in-a-vat experiences a perfectly realistic virtual world. He could have experiences of going to the beach on a sunny day, meeting friends, being stuck in traffic, or being home alone, watching videos about philosophical topics. Is there anything you could point to, in your present experience, to prove that you aren’t a brain in a vat? It won’t help to pinch yourself. The local feeling of pain, is just the kind of sensory signal that the supercomputer can easily supply the in-vatted brain. Typical skeptics don’t try to prove that you actually are a brain in a vat, they will argue instead that it’s bad enough that you just might be, but you can’t tell the difference. Even if you are in an ordinary physical world, watching a video, and actually looking at a hand in front of you — we call that the good case — it’s a problem that your experience feels just like the experience of the brain-in-the-vat. He doesn’t know that his hand is in front of him; he’s just a brain. He doesn’t even have hands. We call this the bad case. So, even if you are in the good case, and your experience really is coming from looking at your hand, You’re just lucky that you’re not in the bad case. You can’t prove that you aren’t, and your inability to rule out the bad case means that you don’t actually know that your hand is really there in front of you. The dreaming argument the evil genius, and the brain-in-the-vat scenario are known as “global skeptical scenarios.” They raise doubts about virtually everything you would ordinarily take yourself you know. But skepticism doesn’t have to be global. You can raise skeptical worries about some particular range of knowledge. For example, you can worry about your knowledge of the past. What if the whole universe just came into being five minutes ago, complete with fossils, antique-looking furniture, and your own apparent memory traces? If it did, it would look just the way it does now. But many of your beliefs, like your beliefs about what you did last summer for example, would be false. In a more restricted, local skepticism, we can raise skeptical worries about knowledge of single facts, just by thinking of some possible way in which things might fail to be as they appear. Consider Alice, who’s walking down the street and wondering what time it is. She glances up at the clock, and sees that the hands show 4:30. Suppose that’s right, and that the clock is working fine. Ordinarily, we’d say, “Now Alice knows that it’s 4:30.” But if we highlight something that could have gone wrong — sometimes clocks are broken — and Alice didn’t look long enough to be sure that the hands were moving, then it gets harder to see Alice as really knowing the time. If her quick glance isn’t enough to tell a difference between a working clock and a broken one, then how does Alice really know what time it is? Just thinking about the possibility of error can make it seem like knowledge is really hard to attain. Do we always have to double check that the clock is working in order to know the time? It’s surprisingly easy to generate doubts about human knowledge, even knowledge of the kinds of things we’d ordinarily consider easily known, like whether there’s a hand in front of your face right now. Skepticism, whether it’s global, or local is an ancient, and difficult problem. Philosophers have proposed various solutions to this problem. The next two videos describe some of the main ways of answering the skeptic’s challenges and defending the idea that knowledge is humanly possible. translated by: Seohyun Yoon(윤서현)

100 Replies to “PHILOSOPHY – Epistemology: The Problem of Skepticism [HD]

  1. Skepticism goes against rational, or rather, concrete knowledge. If one is going to be a skeptic then instead of creating concepts for skepticism on why skepticism is real, they should create an argument as to why they do not believe tangible proof. It's similar to faith and religious. Those lie in a different realm. A 3rd realm if you will, where irrationality becomes rational. In essence, it becomes contradictory and it seems rather self destructive to try to disprove tangible evidence through ones intrinsic views or philosophy. Skepticism is a rejection of clearly present things many times and that's where it loses creditability

  2. Dear Professor Jennifer Nagel: I am hoping that someone will evaluate the incredibly popular philosophical teachings of Dr. Jordan Peterson, the psychology professor of the University of Toronto.

  3. There is a problem with the Brain jar and it's simple. even if the "real" ain't real it do not matter at all what matters is the information it process.
    so to give a example if my brain was in that jar and need to process a experience the experience get processed by my conciseness and it given a information tag.
    this tag is unique to my brain in that jar anyone accessing this tag will experienced it differently so the experience will be unique to me.

  4. I don't see any problem with it. Stuff portrayed in the video is based on "what if…" theory, which makes no sense because you can make same assumptions about anything. Descartes also said "I think, therefore i am" that should create awareness of ones existence. "What if it's all just a supercomputer?" – Well we have no evidences or even reason to ruminate about stuff like that, same goes with question about god, if you can't prove he doesn't exists – it doesn't make it true, you can't prove non-existence of something. That's what skepticism is, video portrayed more like a philosophy view on skepticism.

  5. I'm skeptical of the brain in a vat theory as it presumes with no proof that the computer generated impressions are of equal fidelity, structure, and expressed value to the individual perceiving them :^>

  6. If you cannot tell the difference between a dream and reality there is something wrong with you. Though you may be tricked at first it doesn't take long to figure it out or wake up. I think 'dreams' are one of the weakest alternate realities claim.

  7. ugh why ask stupid questions? because the evil demon made you ask stupid questions. the most useless form of philosophy possible

  8. This reminds me of what I was thinking about when I was 15 years old. Is this like philosophy 101?

  9. Though I enjoy and embrace these kinds of epistemological conundrums, it is obvious that our lives, and the world at large – function in a continuum of condition and consequence.
    For survival's sake we must always direct our attention to these two…

  10. the dreaming argument is just shit. I have experienced dreaming sleep. And It is very different from what I am experiencing now right awake watching your video.

  11. The problem with all of this that we have to deal with what ever reality we perceive. If it's a dream or otherwise. So we can still gather knowledge about that perceived reality. Even if the rules of that reality change at a whim, that would still be knowledge we could learn about that reality. The Basal Assumptions help with this problem and the only way we couldn't use those is if we were solipsist which up til now is unsolvable thus not worth considering until it is solved.

  12. On dreaming… It doesn't matter if you're dreaming or not. You're still in a "reality" of sorts. This world is a dream in a sense because it is entirely sustained by the Creator. It is not the real reality. The Real is God. He's the Real Living One Who never dies. The world, us, we are His creation. We are His actions. We cannot exist on our own. We have nothing on our own. It's only God keeping us in existence. We are contingent beings. If God puts us in one dream or another, it's still "real", it's still what we are experiencing and witnessing through our spirits. Through this experience we can come to knowledge of God, if God wills, and a relationship with God, The Real. It is God's gift out of love. This short worldly life can be an illusion though (if that's what you mean by "dream") if we don't realize God is our Sustainer. In the next life, when we are born there and wake up, the knowledge of reality will be clear to us and we will know what we were really doing in our time on this earth. What we did right and what we did wrong.

  13. You ever had a dream that felt so real, that you didn't realize it was a dream? Of course, we all have.

    Have you ever had an experience so unreal you actually believed you were asleep? Give me a break.

    Wake up people, figuratively. Our common senses (all 5 of 'em) are how we know things, and demonstration is how we teach.

    Sophistry is used to convince individuals that you can't trust your senses, and that you have to trust the authority to tell you what you do or do not know.

  14. This is an easy one. The world goes on regardless of dream-doubt. No amount of doubt will actually stop you from being awake and sitting in that chair. Therefore continue typing. End of problem

  15. I blasted a self-satisfied skeptic about a day ago. He seemed to think introducing a sliver of doubt to any affirmative belief was such an amazing feat. Now I finally understand the positive side of my chagrin. Even before I saw his bland demonstration of skepticism I knew how deceitful it was to toy with a person's firm conviction with endless outliers.

    This video has help me to coalesce my views on the nature of knowledge. Before I begin, let me say that I am not a relativist. Truth is not relative. However knowledge is not truth, it is OUR RELATION to truth. It is important to distinguish an object from your approximation to it. The sun is no less of a sun if you are a hundred thousand miles from it than if you are one inch from it. However our experience of the sun does change with nearness or distance. This is the way with knowledge and truth.

    Knowledge is contextual. Any doubt that attempts to remove knowledge from it's context is not a threat to it's integrity. For example, I know that a circle has no angles. I know this to be truth within GEOMETRY! If you introduce a thought experiment that has me go outside of geometry, I will disallow it. Speaking about the physical wiring of our senses is not geometry. So if you say something like, "How do you know your circle looks like the next person's experience of a circle? Do we all see the same thing or mean the same thing when we say circle?" Geometry require you have visual and or tactile senses to detect properties of shapes, but once you get into the physicality of operational sense organs, you are doing BIOLOGY. Every field of knowledge contains it's own certain knowledge. Knowledge must be self-contained in this sense. It must not escape it's context. This is how you can have certainty. A meta certainty does not exist because a meta certainty is WITHOUT CONTEXT. Remember knowledge is relational. You can not have knowledge to transcend physical propositions. The conceptual is always anchored in the domain of the tangible. Now truth is singular, but to come in contact with THE truth which is supreme over any physical constraint we can imagine, you have to essentially court the Almighty.

    There are not many truths, but many vessels in which to bottle it. Two cups of Atlantic ocean water does not mean there are two Atlantic oceans. Certain knowledge in effect is truth that is dealt with in it's container. Just as it is improper to make your checker piece to behave as a rook or a night, it is improper to solidify a field of knowledge with questions befitting another field of knowledge. There is checkers certainty and there is chess certainty, never the twain shall meet.

  16. Assuming if someone's brain is in a vat, then it must be run by someone. Then how they know they are not in a vat themselves and so on. Also there are so much assumptions here that even if one is not possible then the entire scenario is not possible.

  17. So, is Flat Earth(ism) denialism, credulity, or skepticism? Or all three? Or something else?

  18. If im a brain in a vat then that brain comes from a world ruled by the exact same conditions as mine, since the estimulations the computer or machine is giving can only affect the human brain, so if the so called external world is the same as the supposed estimulated world, and if in the estimulated world there is no way the experiment could be done, then would the theory contradict itself?

  19. So this argument is, if I understand the video: We can't know if reality is reality, so let's not use skepticism and instead just believe whatever we are told? Sounds like this WiPhi is backed by Democrats.

  20. That's why skepticism is best if applied to a certain scope and not to everything. Even then, the results are still worth to be questioned and tested again, since life itself is a big test.

  21. This reminds me of free will.

    Imagine two universes. A world of free will and one without.

    How can you tell the difference?

  22. The problem with the dream scenario is that dreams are consistently inconsistent. Almost every time I dream, it's a different adventure. In contrast to waking up, I have the same responsibilities.

  23. I could be a brain in a jar but there is no evidence that I am so I don't need to prove that I am not … this is called a negative and I don't have to prove I am… Just like the existence of god it can be dismissed as a negative. Not to mention Occam's razor.

  24. I literally had 2 dreams within a dream, both were "normal" life and then i woke uo when i saw something unusually strange. So it can be same with this "reality",i just didn't saw something unusually that would wake me up, yet. Knowledge is possible if you accept assumptions that knowledge is based on. If assumptions are wrong, knowledge is wrong.

  25. You can learn if you are dreaming by pinching your nose and trying to breath through it. If you are able to breath through a pinched nose, you are dreaming. But I still get the argument if its changed to "some kind of alien simulation".

  26. the real problem of skepticism is too many pretend to be skeptics but believe a god exists…. I now I'm awake and feeling the weight of my 14 lb cat on my lap

  27. Humans don't know anything. It's all guesswork and logic is the ability to reduce the waves of chaos that our sensory impressions feed us into tangible patterns that may then be brought under control. Even when we think we know, it is still just a good theory and an unexpected event may at any time reveal to us a new side of that reality which we thought we had under full control.

    Moral of the story – try to keep an open mind. Easier said than done.

  28. "We are all aware that the senses can be deceived, the eyes fooled. But how can we be sure our senses are not being deceived at any particular time, or even all the time? Might I just be a brain in a tank somewhere, tricked all my life into believing in the events of this world by some insane computer? And does my life gain or lose meaning based on my reaction to such solipsism?" – Project PYRRHO, Specimen 46, Vat 7 (Subject termination advised), Sid Meier’s Alpha Centauri.

  29. Living inside a simulation inside a simulation inside a simulation is not a problem. The problem is why I keep existing in this simulation, which I didn’t win any lottery yet? (Because I’ll win in the future!)

  30. Raising hypothetical scenarios that can't be solved is simply useless. It's like asking "when did you stop beating your wife?" If you play the game, and answer it, you lose.

  31. I experience things. Fact. Doesn't matter if I'm a brain in a vat or if it's an "illusion". I still experience what I experience.

  32. Emo Philips: “I used to think that the brain was the most wonderful organ in my body. Then I realized who was telling me this.”

  33. To all those who refuse to see this as a problem, or believe skepticism is irrelevant, just know I'd rather be Socrates dissatisfied than a fool satisfied.

  34. Ah, a video about radical skepticism! That's why we don't make decisions on absolute certainty but on reasonable/maximal certainty.

  35. So she gives a bunch of outlandish what if scenarios or at least ones that were invented by other philosophers supposedly and that's supposed to be proof that skepticism is wrong?… I don't think you know what skeptic is. Being skeptical doesn't mean you have to doubt every single little thing that you know it's all about the probabilities and the physical evidence that's presented to you is what matters to a skeptic.
    Sure anybody can be wrong about anything but I can be wrong that there isn't a pink elephant that's a visible looking at you right now that only I know exists but just because there's an extreme small chance that might be possible doesn't mean I should have to take that claims seriously because that's what being a skeptic means. It means to have a healthy amount of Doubt. Not To doubt every little thing that you know just because of the most marginal possibility​ that might be true because that's a waste of time. Great job forgiving religious people more reason to stay stagnant in their own ideas just because someone said skepticism is a problem.

  36. What I would say about the topic is that what you have learned can’t always be used So what you do is to use what is in front of you like with the clock. If you go outside all the time you will somehow get a sense of time. But you might be wrong because it is not exactly the same time but that is okay. What I use is common sense and educational guess and somehow you get at lease a 50% chance that you might get it right. And believe in a past life where I have already stored knowledge like daja vou where you feel you have already been there before. So strongly disagree of Skepticism sorry that is life get over it and learn and that does not include school of any sort.

  37. To assert that knowledge is impossible is a contradiction in terms. I understand the problem, but one purpose of philosophy is to help us realize the 'good life' and the 'Just city'. Skepticism is absolutely necessary for the scientific method, but at the same time, I believe it can leas to a kind of cognitive paralysis. On the other hand accepting any premise as knowledge leads to neurosis. What then is the most, dare I say "pragmatic" approach?

  38. Even if we live in a simulation, couldn't we still scientifically discover facts about this simulation? (Like the Law of Gravity)

  39. you're not making any sense.
    if we were dreaming, we would be tricking ourselves into believing we exist in world A, but only dreaming that we exist in world A when in fact we exist in world B and are dreaming we exist in world A without ever experiencing world B. and this is all based off of our world A perception of the mind state we call dreaming that we already do in world A.
    and when we consider how inconsistent our dreams are (I've basically been Superman in a dream before) compared to the world we refer to as reality it makes no sense to assume that our reality is, in fact, a dream based off of the suspicion that we may be in a dream or a simulation. I think the problem here is that you're trying to apply the word "dreaming" to something that it is not the definition of.

    how can you assert knowledge to be impossible without first possessing the knowledge to determine that knowledge is impossible?

  40. 8:30/9:03 Black and White fallacy
    Just because she has too look at the clock more longer than looking at it for some seconds. Doesn't mean that she needs to share at the clock all day. Because
    It only means that she needs to look at the clock long than a few seconds to know that the clock is ticking.

  41. If reality is doubted, that our brain is in a vat… super pc… so who put my brain in there and who created the PC? This shit is retarded.

  42. Christian God or absurdity. presuppositional apologists have proven it. see Bahnsen vs Stein debate

  43. Alternatively the clock could be 1, 2, or more hours back or forwards, given that time is an actual concept.

  44. What's the opposite of skepticism? Isn't all this just as much a problem for the opposite of skepticism as it is for skepticism?

  45. I would like to argue that axiomatic conclusions such as 2 + 3 = 5 cannot be doubted, as they are reached by reasoning and reasoning alone.

  46. Until someone can adequately demonstrate that we are a brain in a vat, there's no reason to disprove it. Since it is asserted without proofs, it can also be dismissed without proofs.

  47. All of these examples are in the context of a physical body of some sort. Once you leave whatever body you believe you're in, everything goes out the window! I've seen it. Totally different world but its where the physical comes from.

  48. "Men educated in [the critical habit of thoughts] are slow to believe. They can hold things as possible or probable in all degrees, without certainty and without pain. They can wait for evidence and weigh evidence, uninfluenced by the emphasis or confidence with which assertions are made on one side or the other. They can resist appeals to their dearest prejudices and all kinds of cajolery. Education in the critical faculty is the only education of which it can be truly said that it makes good citizens.”

    ― William Graham Sumner

  49. Scepticism is self defeating. If knowledge is imposible how did he came to that knowledge? We should doubt everything? I doubt that.

  50. After all philosophy I realised that watching YouTube videos on philosophy adds very little to no knowledge… Thinking to ourselves adds more knowledge

  51. 00:20 The problem of skepticism… what do you really know? Are you dreaming?
    00:50 Ancient Greece has two great skeptical traditions: Academic Skepticism and Pyrrhonian Skepticism.
    01:05 Academic Skeptics argued that sensory perceptions don't actually enable you to know anything. Knowledge of the world is impossible for humans. For example, perhaps you are dreaming or perhaps your sensory organs have fooled you.
    01:54 Pyrrhonian Skeptics went one step further. They continued inquiring everything without reaching any conclusions at all. Even the question of knowledge itself was left open.
    02:25 The dreaming argument. How do you know you're not dreaming?
    03:02 Rene Descartes suggested that even if you are dreaming, you should still be able to know a square has 4 sides. But Descartes even questioned that. It simply "feels" right.
    03:40 Descartes formulated an "evil demon"/"evil genius" argument where an evil genius is fooling your sense perceptions and even basic things like your mathematical intuitions.
    04:40 The "brain in a vat" argument illustrates a brain that is controlled by a supercomputer that generates simulated experiences.
    06:03 Typical skeptics don't actually argue that you are a brain in a vat. For them, the possibility of the scenario is problematic enough in itself.
    07:08 These 3 arguments: “Dreaming Argument”, “Evil Genius”, and “Brain-in-a-vat” are known as “Global Skeptical Scenarios”. The raise doubts about virtually everything.
    07:15 Skepticism doesn’t have to be global. It can be local skepticism as well.
    07:27 For example, you can worry about your knowledge of the past.
    07:56 Single fact skepticism can be about particular knowledge. For example, a quick glance at the clock may not be enough to determine if the clock was actually working when the time was read. Does this person really know? What is the probability of error?

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