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0:00
[Music] Hello, dearest friends, and welcome to the second section of Part 6. If you haven't watched the first section, please do so immediately in order to get the fullest picture and avoid any confusion. I'll include the respective link in the description below. In the last section we overviewed two theories of knowledge, one ancient and one modern. They belonged to Plato and Descartes, respectively. In the present video, we will investigate two separate, yet very closely related, reactions
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to Plato's and Descartes' epistemologies. These reactions belong to the British school of empiricism. As a general rule, the empirical tradition claims that sense experience plays a key role in the acquisition of knowledge. So, in stark opposition to Plato and Descartes, the empiricists we will discuss next, insist that knowledge is simply impossible without our sensorial capacities. Historically, one of the first empiricist philosophers who questioned the rationalist
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paradigm of epistemology was John Locke. Locke could not accept that our concrete experience of the world is so flawed or unreliable that cannot be conducive to knowledge. He argued that, on the contrary, our five senses are crucial whenever we claim to know anything. Since, as he puts it, "there is nothing in the mind except what was first in the senses," knowledge without experience is impossible. But how exactly is knowledge gained, according to Locke? There seem to be several stages.
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At birth, says Locke, our mind is like a clean sheet (or tabula rasa), upon which sensations write information, so to speak. Subsequently, similar sensations give rise to specific memories, and later, as time goes by, similar memories beget ideas. What's important here is that knowledge either comes directly from the senses or is indirectly built upon their input. Let's be more specific and look at the previous wax example, but this time from Locke's perspective.
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Unlike Descartes, Locke would say that nobody has any preexisting knowledge about or inborn ideas of wax as an object, for instance, extension. If we imagine a baby picking up a piece of wax and playfully examining it, Locke would argue that in that moment the baby's sensations inscribe certain data on her mind about this particular thing. Next, when the baby is a bit older and able to speak, if someone showed her a similar piece of wax and asked what it was, she would reply: wax.
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That's because, Locke would explain, her mind has come to know what wax was after repeatedly coming into contact with it and memorizing (probably unconsciously) its physical qualities. Going further, if you imagine the same baby a bit older and studying physics in school, she would certainly understand when the teacher tells the class that wax can be molded in different shapes. For Locke, that happens because the mind is able to abstract (or infer) from all the memories
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of various wax shapes the existence of a general notion of shape. However, without those memories - and thus without the sensations that created them - the notion of shape would be meaningless. The same holds true when the teacher says that wax melts at a certain temperature and changes its colour when heated. The reason why the teacher does not explain what colour and temperature are, is because by that age it is assumed that everybody knows those two words.
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And everybody knows what they are, not because we have been born with these notions in our head, but rather because we've been constantly exposed to objects or materials of different colours and temperatures. Then, our mind memorized the sense experience of say, red and hot, to take two random examples. And gradually, as we acquired the memory of many other colours and temperatures, our minds developed the capacity to grasp immediately the generic notions of colour and temperature.
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That is why Locke fundamentally disagrees with Descartes who holds that an object like wax is defined as having, first, an essence (once again, extension), whose understanding or meaning is inborn; and second, some accidental properties which are perceived through the body. Rather, Locke argues that whatever knowledge we get, comes initially and primarily from the senses. Regarding such abstract notions as extension or colour,
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they would be meaningless without having repeatedly seen objects of different dimensions or various particular colours. Against Descartes, Locke's position is that the mind arrives at knowledge through inference from past and recurrent sense experiences of multiple objects in the world. In conclusion, Locke's epistemology states that true knowledge is possible and in the process of acquiring it, the senses play a fundamental, active, and ongoing role.
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By contrast, the mind is secondary in importance and mostly passive. Its main function is to infer knowledge through ever growing degrees of abstraction. However, the next philosopher we'll discuss, although agreeing with Locke in most respects, claims that true, thorough knowledge remains an unattainable ideal. The philosopher I'm talking about is David Hume. In his "Treatise on Human Nature", he agreed with Locke that reliable knowledge comes only from experience.
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But unlike Locke, he insisted that our factual knowledge of the world is never absolutely certain. In this sense, he came to oppose, not just Descartes' rationalist epistemology, but also the idea of scientific truth. For this reason he's remembered as the exponent of modern epistemological skepticism. But how did Hume defend such a discouraging position? His starting point, just like Locke's, is that all knowledge is ultimately based on experience.
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Yet contrary to Locke, he holds that experience consists of two types of perception: impressions and ideas. Impressions include sensations and emotions, whereas ideas are "faint images of [impressions] in thinking and reasoning." Hume also divides ideas into simple and complex. As he puts it, "every simple idea has a simple impression which resembles it." A simple idea would be that of heat or hardness or colour. Complex ideas are derived from the combination of certain impressions.
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A good example would be the unicorn, the idea of which we form by mentally combining the impression of a horse with that of a sharp, cone-like horn. According to Hume, this composite of sensations and emotions, on the one hand, and ideas, on the other, constitutes the only basis of knowledge. Three consequences of Hume's empirical epistemology interest us at this point. The first is Hume's surprising thesis that the notion of "object" is essentially erroneous.
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What we actually experience, argues Hume, is not the object itself, but only impressions of its weight, shape, consistency, colour, temperature, taste, smell, and so forth. The same thing can be said about the notion of self, which is the second major implication of Hume's epistemology. The Scottish philosopher directly attacks Descartes' definition of the human person as a thinking thing, and to the horror of the Christian church, he additionally denies the immortality of the soul.
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His argument went something like this: we cannot know our own mind other than through our sensations and perceptions. Moreover, we never perceive such entity as the "mind." Instead, what we do perceive are series of memories, feelings, and ideas. Then, we somehow assume that there is something called "mind" which encompasses all of these internal contents. But this assumption has absolutely no reality, according to Hume.
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The mind (or the self) is either a conventional name with which we associate all our inner sensations, emotions, and conscious experiences; or the sum of interconnected ideas passing through our consciousness. The main point to remember is that, rather than a separate entity that exists in itself as Descartes believed, Hume came to the conclusion that there is no self-standing mind behind all processes of thought. Thirdly, having attacked the existence of an independent mind,
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Hume casts doubt on the notion of causality. Why causality in particular? Because in his day (as in ours) this notion was central to any branch of scientific knowledge. Ever since they emerged on the scene scientists in all domains have been primarily interested in the causes of natural phenomena, otherwise known as the "laws of nature." For instance, when Isaac Newton asks, why does an apple fall to the ground when I drop it, his answer (accepted by pretty much every
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serious physicist after him) is: due to the law of gravity. What causes the apple to fall down is the gravitational force of the earth that pulls the fruit downwards. Similarly, in biology the theory of evolution inquires into the causes of life on earth. Illnesses also have causes and their discovery is the noble task of the medical sciences. Comparable examples can be taken literally from every scientific discipline you can think of.
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Hume's discomforting reminder is that we never perceive laws of physics per se. We don't walk around and see causes giving rise to effects, or forces pulling and pushing on objects. What we do perceive, says Hume, are events (or what he called "matters of fact") that follow one another. And when we see one event following another event a few times, we become accustomed to this sequence and believe that it will always occur in the exact same manner.
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We then think that there must be some necessary causal relation between the two events. That there must be something like a cause which always and necessarily leads to something like an effect. Hume claims that these two words, "always" and "necessarily," are figments of our imagination, rather than something real out there in the world. Causal relationships, Hume cautions us, are just ideas in our mind. They are not facts about the world. Let's take a simple example, sunrise.
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We all know that the sun rises in the east and does so every 24 hours. But how do we know it? By simple observation. We actually see the sun rising in the east or, on cloudy days, we know the sun is up there because there's light outside. Here, it is crucial to keep in mind that the phenomenon of sunrise is factual, i.e., it is based on our visual experience. Hume would say that as we witness the sun going up every morning,
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we start believing that there is a causal relationship between sunrise and morning. Even more, we assume that the sun will continue to rise indefinitely. That's exactly what Hume finds problematic. He remarks that there is no absolute certainty that the sun will rise every day until the end of time. Sunrise is a mere factual truth based on recurrent past experience. It is not an enduring truth, valid anywhere and anytime (like the statements of mathematics).
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There is no endless objective necessity by virtue of which a cause called sunrise will lead to an effect of a new day. Nothing whatever can guarantee that the sun will keep rising forever. The possibility that it may not rise at some point in the future, no matter how distant, is real. Our error, at least in Hume's eyes, is that, by seeing the sun rise in the east every single day it becomes a custom of our mind to think that it will regularly and necessarily rise every day.
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Moreover, scientists themselves jump to the conclusion that there is an objective law which governs the behaviour of the sun and causes it to rise in the east, putting an end to the darkness of the night. Hume thinks this is wrong. It is wrong because what science does is abusively impose upon a sequence of phenomena a "law" of which we can never be 100% certain. For Hume, this epistemological move is unwarranted. What we call "law" or the proposition that this cause has this effect,
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is a mental trick through which we unwittingly impose coherence upon our fundamentally incoherent experience. In fact, what happens in reality is that we just witness one phenomenon (the night) being usually followed by another phenomenon (sunrise). Hume's point is that we have no absolute guarantee that the same sequence (night-day, night-day) will occur unaltered in future experience. Therefore, the concept of "natural law" should never be confused with
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our subjective, customary perception of a certain sequence of events. "Necessity" and "custom" are two fundamentally different notions. Hume concludes his theory by saying that science is not the realm of irrevocable certainty, but only of temporary probabilities. Note that he does not argue that knowledge is not possible at all. His position is that to the extent that our knowledge is fundamentally factual, i.e., based solely on sense experience, it will always be both limited and temporary,
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that is to say, merely probable. None of us, not even the most insightful and gifted scientists, can ever be absolutely and forever certain of the truth of any statement about the world. Any factual statement or scientific hypothesis is at best only probable. Hence, the final conclusion of Hume's epistemology: what we can hope for is just probable knowledge of experience but not necessary, irrefutable, and timelessly accurate knowledge.
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That is why, according to Hume's epistemological skepticism, not even science can ever become the most reliable source of knowledge. Science is merely a human reaction to experience, one of any number of other, equally plausible, reactions. Another plausible reaction would be religion to the extent that religion declares God to be the creator (or universal cause) of everything in existence. Of course, science denies God as absolute cause, but replaces him with the notion of
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universal causality manifested through so-called natural laws. Yet, both science and religion see causes where there are none, at least not objectively, i.e., outside human experience. In this way and ironically enough, although a declared atheist, David Hume managed to drive a pretty big stake through the heart of science. But did he have the last word on the possibility of human knowledge? Happily enough, the answer is a definite "no".
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And that's thanks to one of the greatest minds in the history of Western philosophy, Immanuel Kant. In the next video, I'll try to explain why Kant's epistemology succeeded in overcoming Hume's skepticism. I hope to see you then. Thanks so much for watching. [Music]
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