 Hi, I'm Peter Adamson, and you're listening to the History of Philosophy podcast, brought to you with the support of King's College London and the Leverhulme Trust, online at www.historyoffilosophy.net. Today's episode, Nobody's Perfect, the Stoics on Knowledge. When we last left our hero Chrysippus, he was grappling with two formidable opponents, the Sorites paradox and the Lyre paradox. To remind you, the Sorites goes like this. I ask you whether one grain of sand is a heap of sand. You say no, so I ask about two grains then three, and so on. As soon as you admit that the threshold has been reached so that we finally have a heap of sand, I say, that's ridiculous. Adding one grain of sand can't turn the amount into a heap. A variation, which touches on a sensitive spot for me personally, asks you to imagine plucking hairs off a man's head one at a time until he becomes bald. It's absurd to suppose that one hair could make the difference, yet he surely becomes bald at some point. It's a cute little paradox, but does it rise to the exalted level of being philosophy? As it turns out, this puzzle, and others like it, provoke a lot of excitement among philosophers nowadays. They raise the issue of vagueness. There are certain concepts which seem to have no sharp boundaries, like bald and heap, as the puzzle illustrates. Those are, if you'll pardon the expression, particularly clear cases of vagueness, but they are far from the only ones. Think, for instance, about evolution. Apes turn slowly into humans generation by generation. Is it any easier to say which generation separates ape from human than it is to say which strand of hair separates hirsute from bald? Probably not. So human seems to be a vague term, and presumably all our other biological concepts are too. Concepts of man-made things, like tables and airplanes, look even more obviously vague, likewise for colors and other qualities like thin and fat. The more you think about it, the vaguer the world seems. Philosophers can hardly avoid being interested in this once they've noticed it, and have tried to develop more precise notions of vagueness, hence the fascination of the Ceraites paradox. Chrysippus was apparently the first to feel this fascination. He wrote entire treatises on the paradox, and, thus, has some claim to be the first philosopher to deal with the topic of vagueness. Sadly, these works are lost. We know only from later reports that his way out of the paradox was this—simply fall silent before it becomes unclear whether the sand is a heap. If things start being unclear at about twenty-five grains, then, when you are asked about the twentieth grain of sand, just say nothing at all. Refuse to be drawn on the issue. Now, despite occasional claims to the contrary, this does not seem to constitute a solution to the Ceraites paradox. It's only a strategy for approaching the dialectical game the paradox envisions. In order to avoid falling into an absurdity, Chrysippus advises you to just keep your mouth shut. As Cicero says in reporting the strategy, you will be like a chariot driver pulling up his horses before running off a cliff. Notice that Chrysippus tells us not to be silent the first time we are unsure, but before we start to be unsure. His goal is purely defensive. He just wants to help us avoid saying something false or something absurd—for instance, that twenty-four grains of sand isn't a heap, but twenty-five grains is a heap. This may strike us as a bit disappointing. We were hoping to learn something about the problem of vagueness, but Chrysippus's advice seems to be simply, don't go there. The liar paradox also prompted him to write a whole series of lost treatises, and again, his aim was apparently to prevent any contradiction or absurdity from arising in the first place. As far as we can tell, his solution was to claim that a statement like, I now truly say that I am speaking falsely, is not a genuine proposition, though it appears to be one. It's just not the sort of thing that can be true or false. But why should Chrysippus have devoted so much energy to these paradoxes, especially if he was satisfied with a defense that would fall short of a solution? Surely the puzzles appealed to his natural gift for logical analysis. But just as surely, he had a broader philosophical project in mind. As I said last time, he inherited from Zeno, the founder of the Stoics, an ambitious theory of knowledge. This theory envisioned the possibility of a perfect sage who would never make a mistake. That's not to say that Zeno himself was such a sage, or that he knew where to find one. The Stoics sought only to defend the theoretical possibility of the sage. They weren't committed to the idea that there actually are or ever have been any. What's the point, then? Of course, it's a philosophical one. Without the possibility of faultless rationality, there is no standard against which we can measure ourselves. One of the main dramas of Hellenistic philosophy was the opposition between the Stoic's extreme optimism and ancient skepticism. The ancient skeptics, as we'll be seeing in later episodes, argued that all candidates for knowledge seemed to involve some uncertainty. The battle lines were drawn. The Stoics claimed that certainty is possible, the skeptics that it is not, or more modestly that as far as we can tell, it is never achieved. Here we need to be careful, though. The Stoics were not saying that we can be certain about everything or that the sage would know everything. Rather, they were saying that the sage would have certain knowledge in some cases and that he would be able to tell the difference between certainty and doubt. In cases of doubt, he would refrain from making any judgment at all. This explains Chrysippus' answer to the Serites paradox. That's a classic case where doubt is thrust upon you. Chrysippus' response, and the sage's response, would be to fall silent to avoid committing oneself. The idea of suspending judgment is also at the heart of the skeptical project. Indeed, we can sum up the difference between the two schools by saying that the Stoics thought we should suspend judgment when we are not certain. The skeptics agreed, but added that as far as we can tell, certainty is never available, so we should always suspend judgment. All this means that Stoic epistemology revolves around the task of showing that we can have certainty. In this, the Stoics are returning to a project dear to the hearts of Plato and Aristotle. They want to distinguish between true knowledge or understanding and mere opinion. The Stoics lay it on pretty thick when it comes to making this distinction. Those who have opinion and not knowledge only get at the truth by being lucky. After all, they lack certainty, so they could just as well have been wrong. So the Stoics compare them to insane people. Or perhaps I should say the Stoics compare us and themselves, anyone who is not a sage, to insane people. This may itself sound a bit crazy. And actually, the Stoics do think some non-sages are better than others. Those who, like the Stoics themselves, are at least trying to achieve certainty are better than those who let their beliefs run out of control, endorsing any thought that comes to mind. Where, then, is our certainty going to come from? Like the Epicureans, the Stoics point to sensation. All our knowledge is ultimately grounded in our sensory experiences, since it is the senses that give us access to the physical world around us. This is unsurprising given that, again like the Epicureans, the Stoics believe that only physical bodies exist. They call the sensory impact of bodies on us impressions. An impression would be the way things seem to be to you. For instance, if you walk into the kitchen and smell coffee, you're having an impression that coffee has been brewed. As we've seen, the Epicureans express total confidence in such sensory experiences. They think that all sensations are true, even if we put the wrong interpretation on those sensations. The Stoics are more skeptical, if you'll pardon the term. They would say that some impressions are true, but some are false. Perhaps the kitchen smells that way because someone spilled the coffee grounds on the floor. Part of the debate here concerns the question of what sensation is telling us. For the Stoics, your experience makes it seem to you true that coffee has been brewed. For the Epicureans, it presents only the smell of coffee. It is you who adds the delightful, but possibly false, inference that coffee actually awaits you. Of course, the Stoics are not saying that you, or much less the sage, are forced by your senses to believe that there is coffee in the pot. But, they analyze the mistake differently. For them, you have from your sense of smell the impression that there is coffee, but it is up to you whether to assent to that impression. You could reject the impression, for instance because you also see spilled coffee grounds on the floor. Or, you could do what the sage does, and suspend judgment until you are absolutely sure, for instance because you have actually poured the coffee and tasted it so that you know it really is coffee. Now, I know what you're thinking. If some sensory impressions are false, then how can sensation provide certainty? The answer is simple. Though some impressions are false, some are true, and some are so obviously true that they could not be false. The Stoics call these special experiences cognitive impressions. These are the impressions in which we securely grasp something. That metaphor of grasping lies behind the Greek used by the first Stoics, phantasia cataleptice. This grasping word catalepsis was translated into Latin by Cicero using the word cognitio, which is why we call them cognitive impressions. I mention this in part because ancient languages are cool, and in part because the word cognitive might otherwise mislead you. The point is not that other impressions have nothing to do with thinking or cognition, but that other impressions are such that they might be false. A cognitive impression is rock-solid and can serve as the basis for certain knowledge more generally. Zeno gave a vivid analogy to illustrate this theory. He held out his open palm and said that this represents the mere impression, the way things seem to you. Then he put his fingertips together and said that this is assent. It is agreeing that things really are that way. Next, he formed his fingers into a fist and said that this was the cognitive impression. The fist indicates that one has a firm grasp so that one is assenting to something that must be true. Finally, he placed his other hand over his fist and said that this represents knowledge. Notice that the cognitive impression is not yet knowledge. It is rather the basis for knowledge. We achieve knowledge only when we are systematic, when we combine together many rational impressions into a global understanding of the world. To understand that understanding, we need to retrace our steps. Go back to the most basic stage, the impression. Our entire experience is made up of impressions. The exact manner in which we receive them was a matter of debate among the early Stoics. Taking a leaf from Plato's Theaetetus, the earliest heads of the school, Zeno and Cleanthes, argued that the impressions are really like imprints made in wax. Chrysippus disagreed, pointing out that we can receive and retain many impressions all at the same time, something impossible in the case of wax. Still, all the Stoics were committed to the idea that impressions have some physical realization. After all, according to them, nothing nonphysical exists. Next is the stage of ascent. The Stoics believe that this capacity for ascent is already a great gift, something that differentiates us adult humans from animals and small children. It is, you might say, the core of rationality. A beast can experience that the world seems a certain way, but only a mature human can take a critical stance regarding the world and say to himself or herself, well, things may seem this way, but I'm not so sure. Ideally, the human will remain self-consciously unsure unless there is certainty, which arises only through a cognitive impression. It is not only sages who can have such impressions. According to the Stoics, even children have such impressions. Your impression that you are listening to a podcast right now might count as such an impression. There's no way you could be wrong about this. Or, if you don't like that example, then your impression that it is daylight when you walk outside and the sun is shining. You just can't be wrong about that. However, it is possible to improve oneself in this respect. The Stoics speak of the cognitive impression as being technical or artistic, by which they mean that our knowledge and beliefs inform the way we have experience. I look at someone and see that they have a yellowish complexion. The doctor looks at the same person and sees someone who has jaundice and quite likely a liver disease. Thus, we can expect that with increasing wisdom comes an increase in the extent and detail of our cognitive impressions. By the same token, knowledge helps us relate cognitive impressions to one another. Or, we might even say that knowledge just is grasping the interrelation of cognitive impressions. To do this, one makes use of what the Stoics call preconceptions. For the Epicureans, the word meant rough and ready concepts, but for the Stoics it means the reliable beliefs that arise for all humans through careful observation of the world. This allows us to put our impressions within a more general framework. The sage, of course, is the one whose framework is beyond reproach. He has maximized his opportunity for having cognitive impressions informed by expertise, and is always careful not to leap to conclusions in cases of even slight uncertainty. It is, I think you'll agree, a nice theory, but the ancient skeptics pointed out its potentially fatal flaw. A house is only as strong as its foundations, and for the Stoics, knowledge is built upon the foundation of cognitive impressions. The skeptics showed up with the dynamite for exploding that foundation. They pointed out that any impression, no matter how apparently reliable, will be indistinguishable from some possible misleading impression. Suppose you see your best friend standing before you in good lighting conditions. You will have no hesitation in assenting to the impression that your friend stands before you, but isn't it just possible that your friend has an identical twin? Your friend has kept this twin a secret from you, or they were separated at birth, so your friend doesn't even know this twin exists. Okay, the possibility is remote, but it cannot be totally ruled out, so there is some possibility that you are seeing not your friend, but your friend's twin. The skeptics say that this problem is general and inescapable. There is no impression so convincing that it eliminates all possibility of error. Faced with this, the Stoics could have gone two ways. One would be to say that cognitive impressions do lead us to the truth so that we are guaranteed to be correct in assenting to them, but that perhaps we do not know which impressions are cognitive. This would be, to put it in modern jargon, an externalist solution. From outside the situation of the person judging, we would say the person did have knowledge because they were assenting to an impression that couldn't be wrong. But the Stoics seem to have been what are nowadays called internalists. They insisted that the person judging must not only be free from the possibility of error, but must know that they are free from the possibility of error, from the inside as it were. So, against the skeptics, they claim that cognitive impressions are distinct, having a special quality that marks them out as utterly reliable. It's clear why they must insist on this. They want to preserve the possibility of the ideal sage who never makes a mistake. It shouldn't be just a matter of luck that the sage always gets things right. Rather, he gets things right because he knows that he is assenting only two cognitive impressions, which are always reliable. In other cases, the sage will play it safe and suspend judgment. He will, that is, avoid assenting to impressions where there is room for doubt. Of course, the skeptics say that this will mean never assenting to any impressions, since there is always room for doubt. A lovely, though no doubt apocryphal, story about a Stoic named Spherus illustrates the difficulty facing the Stoics. While the guest of a royal court, Spherus was served wax pomegranates as a practical joke. When he tried to eat one, the king mocked him for assenting to a false impression. But Spherus replied that he had assented only to the impression that it was reasonable to suppose these were pomegranates. It would also be reasonable to touch on one last question regarding Stoic views about belief and assertion. Suppose I say, this giraffe is a majestic beast. How do we account for the fact that this string of English words, or any string of words, connects with the world around us? It's the most fundamental issue in the philosophy of language, and the Stoics were sufficiently worried about it to devise one of their most original doctrines, the idea of lekhta, or sayables. Remember, the Stoics were materialists. They think that nothing really exists apart from bodies. When I say, this giraffe is a majestic beast, the only relevant body here seems to be the giraffe. But clearly, my sentence doesn't say or mean the giraffe itself. I can touch a giraffe, but I cannot say it. Rather, the Stoics suggest, there is something called a lekton, the sayable, which I have latched onto with my utterance. These sayables form a kind of bridge between language and the world, between the noises coming out of my mouth and the giraffe herself. It would be easy to suppose that sayables are something like thoughts in my mind, but this seems not to be the case. After all, there are many sayable things that neither I, nor anyone else, has said or will say. So, these sayables would seem to be part of the furniture of the world, as it were. But how can this be, given the Stoics' rigorous commitment to materialism? Sayables are not bodies, after all. The Stoics realize this, and see a similar problem in other cases, for instance time and void. These things seem to be required for any complete philosophical understanding of the world, yet they are not bodies. Thus, the Stoics admit that sayables and time and void are some things, but not that they are really real. Or, as they put it with a further bit of technical terminology, they subsist without actually existing. Given the Stoics' materialist credentials, this may seem a surprising concession regarding entities that they themselves refer to as incorporeals. After all, they make a big deal of rejecting such immaterial entities as platonic forms, which for them absolutely do not exist. The difference is that sayables, time, and void are needed to make sense of the physical world around us, whereas forms could never help with this task. They are meant to be causes, but, as the Stoics stress, nothing can be a cause for bodies without itself being corporeal. So, what sorts of causes they accept? What is their understanding of the cosmos and our place within it? Any body who wants to find out should join me next time on The History of Philosophy Without Any Gaps.