As mentioned, scepticism is easy. It’s much easier to knock a building down than it is to build one. And because the Sceptics are only trying to show when knowledge is unreliable, knocking knowledge down and never building it up, the Sceptics can generate their arguments with relative ease. We’ve seen some of these arguments already – those relating to differences in opinions and a lack of universal agreement amongst supposedly wise philosophers – but many of those were rhetorical and not particularly technical. It’s not clear how much depends on them. But the Sceptics have other, perhaps more serious, arguments for their view.
There is no perception, only imagination
The first type of argument undermines the reliability of our perceptions. The Sceptics point out that a perception can come from what originates it, but a perception can also come from what does not originate it. This is a technical way of saying that often what we see is the product of an illusion. In what to us (with the benefit of scientific hindsight) seems like an extremely ironic choice, they use the movement of the sun as an example of this. They say that the sun must be moving at a tremendous speed, as it flies around the Earth, and yet appears to us to be almost still. Our perception of its lack of movement does not come from its being still, but from the distance between us and it, since fast-moving things appear to move slowly when they are at a distance. Our perception (of the sun not moving) does not come from from what originates it, in this case, but from an illusion.
Whilst that example is now known to be false in fact, you can still adapt the argument to suit our context: it seems to us, as we stand on its surface, that the Earth is not moving very much at all, and yet we know that it is flying through space at a tremendous speed. Our perception of the Earth’s stillness does not come from what originates it, because the Earth is not actually still, and so our perception is a kind of illusion.
Less cosmic examples are available. You can see two cups on a table because there are two cups on a table, and you can see two cups on a table because you are drunk and seeing one cup double. (If you don’t want to get drunk to prove this to yourself, you can just cross your eyes or press a finger to one of your eyeballs and you will get the same effect.) In the first case your perception of two cups is coming from the origin of that perception: the two cups. In the second case your perception of two cups is coming from something that is not the origin of your perception: your drunkenness. And so your perception can come from what originates it, or it can come from what does not originate it: I can see two cups because there are two cups, or I can see two cups even though there aren’t two cups. But if perceptions can come from any origin, how can we know when they are coming from what originates them?
Consider optical illusions. A favourite example for the Greeks was a ‘bent oar’. Picture a rower’s oar in the water. Because of the refractive properties of light and water, the oar appears to be at a different angle beneath the surface of the water than it does above. The straight oar looks bent in the water, but we know it is not. Our perception is unreliable. In this case we can correct our perception, but in how many other cases do we take our perceptions without question? I look at a clock and from it infer the time. Do I check the clock is working properly? I watch the news and from it understand current events. But do I check it is not propaganda? How many of the images that we see on social media are true to reality?
You might be thinking: so far, so unremarkable. All this argument really establishes is that direct perception is not a completely reliable way of getting knowledge: you can’t believe everything that you see. But didn’t everyone know that already? And that’s not really a good enough reason to reject all knowledge. In fact, doesn’t it suggest that knowledge is just what happens when we correct our faulty perceptions?
But for the Sceptics, this is just the first step in a more complex argument. All that they mean to show by identifying these faulty perceptions is that sometimes our direct perceptions are true and sometimes they are false. The second step in the argument is to point out that nothing false can be directly perceived in reality. When we ‘see’ an oar bent in the water, we can’t really be ‘directly perceiving’ a bent oar, because there is no such thing: there is no bent oar because the oar is straight. When we see two cups when there is only one, we cannot be perceiving two cups, because there is only one. When we look at two lines of equal length that appear to us to be of different lengths, because they are drawn in a way that gives them some optical-illusory properties, we are not ‘directly perceiving’ lines of different lengths: what we are actually seeing is an optical illusion. The image that makes it look as if the oar is bent, or that there are two cups, or that the lines are of different lengths, this is a product of our brain and our perceptual apparatus and not a product of reality. It cannot be a product of reality, because there is no reality for these false things, so it must come from us. In this way, the image is not a picture of reality, but only a product of our way of perceiving the world. You might say that the image is a product of our imagination. The image is not real, but our brains make it seem real to us. And so a false perception is not really a perception at all, but only an imagining: we don’t really see, we only imagine that we see.
The third step in this argument is to point out that false perceptions have the same character or appearance to us as true perceptions. If I see an actually bent oar, it looks the same as the straight oar in water. If I see two cups, it looks the same as one cup seen double. If I see two lines of actually different lengths, they look the same as the lines of equal length that are subject to an optical illusion. My eye and my brain sees the same thing, and the experience is indistinguishable for me, even though the reality is different.
The false perception, we agreed, can only be a product of my imagination, since there is no reality to be perceived. We can’t be seeing, because there is nothing to see, and so we only imagine that we see. But if false perception and true perception share the same character and appearance, then true perceptions must be a product of my imagination too. True perceptions are a product of the same perceptual apparatus. And so even when we see truly, we only imagine that we see, and by chance we happen to be correct.
But if this is the case, then both false perceptions and true perceptions are the products of our brains. And therefore there are no real direct perceptions, only ever the products of our imaginations. We live in a world of imaginings, not perceptions. And if that’s true then we can never take ‘perception’ as a basis for knowledge, since there is no such thing as perception, only imagination.
In summary: Perception can be true or false. False perception is only imagination. True perception has the same character or appearance as false perception. Therefore, true perception is only imagination.
Clearly the conclusion of this argument has wide-reaching consequences. The bulky edifice of human knowledge seems very shaky if you think of it as being only the product of our collective imaginations. It is no better than a game of make believe, akin to a complex fictional world that has no more claim to reality than what is lent to it by the mind of its possibly insane author.
Most people object to the Sceptic’s argument on the basis of being able to discern a difference in the ‘character and appearance’ of true and false perceptions. We know when we’re seeing an optical illusion, or at least we can know this when we are no longer children. But the Sceptic’s argument is more resilient than you might think. It doesn’t need to depend on optical illusions and other obvious cases of faulty perception. The same point can be demonstrated by considering any everyday instance of two things that appear similar.
Imagine you are playing cricket. (You don’t need to know anything about cricket for this example to work.) You are in the dressing room, about to go out to bat. You pick up what you think is your bat. But, unbeknownst to you, a teammate has the same bat. The bats look the same, they feel the same. You make a mistake. You think you have your bat, but in reality you have your teammate’s. You only imagine that you have your bat. Now consider the alternative scenario: same dressing room, same bats, but this time you pick up your own bat. The experience, for you, is exactly the same. You know no different in either case. But the reality is different. You think you have your bat, and in reality you do have your bat, but since your experience of this is exactly the same regardless of the reality, you are in fact only imagining that you have your bat. This time you happen to be correct, but this reality is nothing to do with your perception.
Consider another example: say you are looking at an identical twin. You believe that you are looking at James, but in truth you are looking at Edward. You have a false perception. You do not perceive James but only imagine that you do. Now say that you are, in fact, looking at James. You have a true perception. But this perception is exactly the same as the false perception of ‘seeing’ James when really you are looking at Edward, which we called an ‘imagining’. But if both perceptions really are the same, which they are, then you can only be ‘imagining’ that you are looking at James. As it turns out, your imagination is accurate in this case. But that doesn’t change the nature of it being an imagining.
And therefore, there is no such thing as true perception, only ever imagination that happens to be accurate. But this leaves accurate perception to be only a matter of chance, and that’s hardly a sound foundation for knowledge.
It is always possible that you are wrong
Even if you could get around this argument and claim that some perceptions really are the product of reality and not the product of our imagination, you could never be really, totally, 100% sure whether you are having such a real perception or not. You might be wrong; how would you know? Even if the character and appearance of false perceptions is not exactly the same to you as the true, the true and the false are near enough that there will always be some room for doubt. And because of this, you can never be sure enough to claim that you ‘know’ you are perceiving reality truly.
As sure as you can be that something is true, it is always possible that it is false and you are wrong. This thought is the launchpad for scepticism with a small ‘s’. It has been an ever-present feature in philosophy, from then until now, and will no doubt (no irony) continue to remain in the future. (I wonder if the certain continued presence of scepticism in philosophy counts as another way that scepticism refutes itself?)
The thought that we might be wrong is a healthy doubt. It is often the first philosophical thought that people have, often when they are children or young teenagers. Do I see the same colours that other people see? How do I know? How could I check or confirm that what I see as ‘green’ is what you see as ‘green’? At every day of my life someone has pointed at grass (and other ‘green’ things) and said ‘that is green’. Perhaps, for all I know, what I see as ‘green’ you see as ‘blue’, but we learnt to call whatever we see by its conventional name. We could be living in totally different colour-worlds! It’s no good saying that we share the same human eyes and are not colour blind, because for all we know you or I have unique eyes, hitherto unknown to science. It might never have happened before, but there’s a first time for everything.
I think I am standing and giving a lecture. How do I know that I am? Perhaps I am dreaming. Perhaps I am hallucinating. Perhaps I have lost my mind and cannot tell memory from reality; perhaps I am sitting in an old-folks’ home, lost in confusion. Perhaps I am a disembodied brain in a vat, hooked up to electrodes that activate the parts of my brain that give me the convincing impression that I am standing and giving a lecture. Perhaps I am in a complex computer simulation.
These kinds of doubts are common enough to be called universal to all thinking people, regardless of culture or philosophical tradition. We find them everywhere we care to look. The Daoist philosopher of the 4th century BC, Zhuangzi, dreams he is a butterfly, flying happy and free, with no knowledge that he is Zhuangzi. He awakes to know he is Zhuangzi who dreamt of being a butterfly. But can he be so sure he is really Zhuangzi dreaming of being a butterfly, and not a butterfly dreaming of being Zhuangzi?
(This is neither the time nor place to introduce Zhuangzi, but since this story constitutes the first opportunity that merits his inclusion in this book I will allow myself a brief aside: In my personal history of philosophy, Zhuangzi deserves his own chapter. He is my prologue, but he lives now, for me, alongside Socrates and the Cynics. His philosophy shares many similarities with theirs. I see them as kindred philosophical spirits. Whilst Zhuangzi presents sceptical views, his philosophy is much more than that. His scepticism is only a tool and a way to get you on the path. It is striking for me that the same conclusion is reached, from two worlds apart: wisdom consists in aligning your will with nature. Be like water. Care nothing for the honours at which the world aims; you only buy yourself debts and burdens. A useful tree gets cut down or else constantly picked at. I dislike so-called ‘comparative philosophy’ for its tendency to clumsily blunder into the imposition of one view on another. I wouldn’t want to repeat those mistakes. All I will say is that if you have got this far and found yourself inclined towards the kind of view expressed by Socrates or the Cynics, you will find a lot to like in Zhuangzi too.)
Western philosophy has worked hard to overcome these sceptical doubts, with varying degrees of success. Augustine of Hippo, writing in the 4th and 5th centuries CE, notes that, in all this doubting, I must at least know one thing for sure: that I exist. Because even if I am mistaken, still I must exist in order to be mistaken. (As he says it, ‘si fallor, sum’: ‘If I am mistaken, I am.’) The 17th century philosopher Rene Descartes takes up this argument and expresses it as his famous ‘cogito ergo sum’: ‘I think, therefore I am.’ Both of these are reasonable refutations of total scepticism, since they establish the absolute first-person knowledge of your own existence – you know that you exist – granted to you by your ability to think, but that is all they establish and in itself that is not all that much. Whilst certainly existing and thinking, you might still be constantly deceived in the content of your thinking, as would be the case if you were a butterfly dreaming of being a philosophy lecturer. You exist, sure, but beyond that you are totally wrong about everything. That still sounds like scepticism to me.
Both Augustine and Descartes (and many, many others in the history of Western philosophy) use the monotheistic God to fill in the gaps. They take their own existence as a foundational starting point, and from there reason towards the necessity of the existence and nature of God, and from the goodness of God infer the general reliability of our perceptual apparatus, since why would a good God makes us such that we are always in error? There is more to say in defence of Descartes, and I will come to him in time in volume two of this series, but even at first glance we can see that placing all of our knowledge in the hands of God is likely to be an unsatisfactory and viciously circular solution. After all, how do I know that God exists and is good? By what method do I come to know these things? By my God-given powers of reason? I know that God exists because reason tells me so; and reason is reliable because God made it so. See how I am trapped in a circle! And what is the poor atheist to do?
Until we find a satisfactory response to our sceptical doubts, we can never be sure that we really know anything at all. Scepticism is free to deny the existence of knowledge. The consequences of this could be disastrous, and could be particularly disastrous for philosophy. If there is no knowledge to aim for, why do we even bother?
There is no difference between knowledge and opinion
This is not so much an additional argument for Scepticism as it is an expression of its wide-reaching consequences. It’s particularly consequential for philosophy. Ancient philosophers understood there to be an important difference between mere ‘opinion’ and real ‘knowledge’. It’s a very intuitive distinction. I might have an ‘opinion’ about how to fly a plane, but since I’ve never flown a plane or been trained to do so, I have absolutely no knowledge of how to do so. Would you want me at the controls of your flight, equipped only with my ‘opinions’? Or would you rather have a pilot who knows what they’re doing?
The difference between the pilot and me is knowledge: the pilot has it, I don’t. It’s an important distinction, easily identified in examples where knowing what you’re doing or saying might have serious consequences. Would you be happy to be launched into space on a rocket built by someone who has no knowledge of rocket building? Would you be happy to be operated on by a surgeon who doesn’t know what they’re doing?
We’ve seen this distinction play out in all of the philosophers that we have covered up to this point. What makes them all ‘philosophers’ is that they are not content to be guided by mere opinion: they want to be guided by knowledge. Philosophy is how they do this: it is an attempt to turn mere ‘opinions’ about how to live well as a human being – which everyone has, no matter how ignorant or unvirtuous they might be – into real ‘knowledge’. This is often done by providing a rational justification for your opinion. It’s not the strength of the opinion but the strength of the rational justification of it that makes the opinion more secure, turning it from mere opinion into real knowledge. We find good reasons for our opinions, and in doing that we transfer the burden of truth onto those reasons and away from our personal opinion. Seeing those reasons, investigating them, understanding them and putting them to the test; it’s that process that turns the ‘mere opinion’ into something more.
Socrates is a good example of this because it’s what he does, explicitly and deliberately. He encounters many people who have ‘opinions’ about important things like virtue, but he finds few with any knowledge. He exposes this by showing that none of them can give him a rational account of how they know what they know. All they can say is something like ‘I heard it from so and so’ or ‘it seems to me that…’, and other unsatisfactory justifications. He investigates these opinions and finds them lacking. He goes looking for the rational justifications for these opinions and finds none, in that way exposing them to be mere opinion and not knowledge. In doing this, he hopes to move closer to real knowledge by investigating the ideas that people have about things.
As we’ve just seen, the Academic Sceptics cut off this Socratic aim by arguing that knowledge is impossible. There is no possibility of offering a comprehensive rational justification for your opinion, and so you can never move beyond opinion and into knowledge. They point out that many philosophers claim to have knowledge, but they all disagree with one another, so they can’t all be right. Many of them think that they have knowledge but in fact they only have opinion; how can you know whether you are one of these? They will point out that no matter how sure you are, it’s always possible that you could be wrong, and therefore your knowledge is never secure. You can never know whether you have real knowledge or just firmly-held opinion. But what made something ‘knowledge’ as opposed to mere ‘opinion’ was precisely that it was made secure in some reliable way. Having pointed out that there is no reliable way to secure knowledge, the Sceptics have collapsed the distinction between knowledge and opinion. For a Sceptic, there is no difference between knowledge and opinion; both are equally insecure. And so what is the point of trying to improve on opinion, if there is nothing to be gained? Perhaps we should remain in the realm of mere opinion and learn to live there as best we can.
At this point I would hope you are beginning to have some anti-Sceptical reactions. Imagine they are correct in what they say and there is no such thing as knowledge, and consequently no difference between knowledge and opinion. Picture this in reality. I say again that I want to fly your plane, equipped only with my opinions but no knowledge. ‘It’s no good asking for a pilot’, I say, ‘because there’s no such thing as knowledge!’ The pilot stands next to me, protesting that they have extensive training and experience and insisting that, really, you must believe them when they say that they know what they’re doing (and that I really don’t). If you take the Sceptics at their word, you would have to say that there is no discernable difference between me and the pilot. But that’s silly, isn’t it? Put us up in the air and you’ll soon see the difference! The pilot will fly safely by whilst I crash on take-off (if I can even get the plane started). It’s not a subtle difference.
But before I slip into offering any more arguments against scepticism, let me say one more thing in their defence. If there is no way of knowing the difference between knowledge and opinion, then there is no such thing as knowledge. But whilst there might not be knowledge, there can be a kind of understanding and acceptance, even if there is nothing to understand beyond our inability to understand. This might sound like hair-splitting wordplay but it needn’t be as vicious as it sounds. Philosophy goes looking for the limits of human knowledge and it’s clear that there must be limits; all that we disagree about is where to draw the line. As Kant says in the 18th century: when philosophy goes looking for the limits of human reason and finds them, of anything that lies beyond those limits, the most we can ask is that we comprehend its incomprehensibility. Kant places those limits at some distance away from our ordinary ignorance and I’m inclined to agree with him; there is a lot that we can know and understand before we hit something about which we can only comprehend its incomprehensibility. The Sceptics just move those limits an awful lot closer. So close, in fact, that these limits are already behind us. We have already transgressed the limits of human knowledge. We have tricked ourselves into thinking we know more than we have any right to know. We should go back to what we know, which is nothing, and rest content with that. We should live within our limits. The most we can understand is our abject lack of understanding.
For me, this invites the obvious counterpoint that we are not so limited as all that. I think I understand more than my own abject lack of understanding. I think I’m right to say that a pilot knows more about flying planes than I do, and if you doubt this then put us both in the cockpit and see what happens. I am comfortable enough to say that I know my own name, I know that 12×12=144, I know that water boils at 100 degrees centigrade at sea level, etc., etc. I know I have feet, or at least I accept this without thinking, as I walk about on them. Am I mistaken to be so sure? Do I misunderstand something, and if so, what? Would a man who seriously doubted whether he had feet (as he walked about on them) be a perfected picture of rationality or a picture of madness?
Many of these examples are borrowed from the 20th century philosopher Ludwig Wittgenstein. He has been mentioned a few times in this book, always favourably. I’ll leave any serious discussion of Wittgenstein’s philosophy for the appropriate time and place (which is planned to be volume three in this series), but in his later work – On Certainty – Wittgenstein suggests a compelling anti-sceptical line of reasoning. In a sense it moves Augustine and Descartes one step further. Just as Augustine realises that in order to play the sceptic and doubt my beliefs, I cannot doubt that I exist, because I must exist in order to be mistaken about my beliefs; and just as Descartes realises that he cannot doubt without existing and thinking, and therefore knows at least that he exists and is a thinking thing; so Wittgenstein realises that there cannot be doubting behaviour without non-doubting behaviour. In order to doubt, some things must be held certain, even if only the meaning of your words or the rational structure of your thought (which is much the same thing). You cannot doubt whether you exist without holding firm to the idea that you must exist in order to be doubting anything at all. You cannot doubt that you are thinking without holding firm to the idea that you are thinking about doubting. The certain knowledge of your own existence and capacity to think is already contained within any doubting behaviour. In that way, the question is not whether these things are true or false but whether it can make any sense to doubt them.
What Wittgenstein realises is that certainty is sometimes built into our understanding from the outset. You cannot question whether 12×12=144 unless you have some understanding of mathematics: you need to know what ‘numbers’, ‘multiplication’, and ‘equality’ are in order to understand the question. But once you have some understanding of mathematics, then you already have your answer, because that language is determined by the set of things held to be true within that language. The language of mathematics is the language of numbers, and in understanding numbers, you understand what it makes sense to say in that language and what it doesn’t make sense to say. In the language of mathematics, it makes no sense to say that ‘12×12=144 might be false’; and so if you do say that then you only show that you don’t understand the language of mathematics. No one who had any mathematical understanding would seriously suggest such a thing.
You cannot doubt whether you have ‘feet’ unless you understand what ‘feet’ are, and you show that you understand what ‘feet’ are when you walk around on them; but in walking around on them you can’t be seriously doubting that you have them. Can you sensibly say: ‘I accept that I am walking about, but how do I know I have feet?’ Life shows us what we know, or at least what we accept as knowledge and not mere opinion. What would it look like for a man to pace up and down as he doubts whether he has feet? Could he take another step? Would he jump into a chair in alarm?
You cannot doubt without holding some things to be beyond doubt; some things must be held firm, like Augustine’s knowledge that he exists and Descartes’ that he is a thinking thing, or the mathematician’s belief that 12×12=144 or the walking man’s belief that he has feet. These have come to be called ‘hinge’ beliefs because it’s as if they are beliefs around which other beliefs swing. And sometimes these ‘hinge’ beliefs necessarily rule certain doubts out of the question. It is not just false for Descartes to think he might not exist; it makes no sense for him to say ‘I think I don’t exist’. Because in thinking, he exists, and is thinking. His certainty of these things is already contained within his understanding of what it means to exist and think. In that way they are shown to be beyond reasonable doubt. Likewise, it’s not just false for a mathematician to suggest that ‘12×12=144 might be false’, it makes no sense to say this. Because in understanding mathematics, the mathematician understands that 12×12=144, and that’s all there is to say. It moves beyond the limits of reasonable mathematical thought to think that anything more is needed here.
I side with Kant and Wittgenstein against the Sceptics. There are limits to reasonable thought, but they must be reasonable limits. The Sceptics, it seems to me, impose unreasonable limits on thought. In leaving everything open to doubt, they leave nothing with which to doubt, yet again finding a way to be their own refutation. We cannot sensibly say that we know nothing. There must be something that we hold firm, even if only the meaning of our words (as Wittgenstein would say), or the fact that we exist and think (as Descartes would say).
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