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  • By the time were done today, I just might have you questioning whether this apple is

  • real or not. Think I can’t do it? Gimme about ten minutes! I might have you wondering

  • whether I’m a physical object or not.

  • And the same goes for all of this stuff, and your computer, and Nick behind the camera! Andyou!

  • How? By unleashing the power of empiricism.

  • [Theme Music]

  • Last time, we learned about 17th century philosopher Rene Descartes, and how he upended the apple-basket

  • that was his entire personal belief system, and descended into a radical skepticism, only

  • to emerge with his conviction that: Cogito ergo sum – I think, therefore I am.

  • This one idea -- the fact that he was thinking -- or really, the fact that he was doubting

  • -- allowed him to build back up, one by one, more beliefs that he thought he could rely on.

  • But in the end, most of the beliefs that Descartes ended up putting back into his intellectual

  • apple-basket had to do with the immaterial world.

  • Like, he decided that he could believe that he existed, as a thinking thing.

  • And he believed that God existed.

  • Ultimately, he lit upon the idea that some of our thoughts are clear and distinct in

  • a way that somehow guarantees their truth.

  • But, a lot of philosophers disagreed. They argued that thinking on its own wasn’t enough.

  • Like, just because youre thinking, doesn’t mean that your thoughts correspond to material

  • reality in any reliable way.

  • Basically, Descartesphilosophical opponents thought that the Cogito was a dead end.

  • So here, we start to see a split between two different understandings of how we can most

  • reliably get to the nature of reality, and therefore truth. Both were responses to the

  • constant questioning that is skepticism. On the one hand, there was rationalism.

  • And on the other: empiricism

  • Descartes, like Plato long before him, was a lover of reason. He met skepticism with rationalism.

  • He believed that the most real things in life were ideas -- propositions that can be known through pure reason.

  • Deductive truths, which we talked about before, fall into this category. And mathematical truths do, too.

  • But by contrast, empiricism is based on the principle that the most reliable source of

  • knowledge isn’t our ideas, or our reasoning, but our senses.

  • Sure, we can know things through deduction and basic logic.

  • But what actually leads us to truth, or at least gives us our best shot at getting there,

  • are things like induction, and the scientific method -- ways of thinking that tell us about the material world.

  • Probably the most famous split among philosophers between these two camps was the life-long

  • debate between Plato and Aristotle.

  • Plato was convinced that Truth resided in the immaterial world of Ideas, while Aristotle’s

  • attention was focused firmly on the ground.

  • But what about in Descartesday? If he was the original prototype of the navel-gazing

  • philosopher -- a living example of rationalist thinkingthen his foil was was the 17th

  • century English thinker John Locke. This is where he was born.

  • Locke believed that were all born as a tabula rasa, or a blank slate.

  • He argued that all knowledge is obtained through experience.

  • He rejected the concept of innate ideas -- the view that were born pre-loaded with certain

  • information, like what’s good versus what’s bad, or what is the nature of God.

  • Locke thought that we are born knowing nothing.

  • And instead, all of our knowledge comes to us through sense data.

  • But one place where Locke agreed with Descartes was in the idea that, just because your senses

  • tell you something, that doesn’t mean you can trust it.

  • After all, sometimes your senses give you false information, like when you think you

  • see or hear something that’s just not there.

  • Descartesresponse to this, of course, was to just throw out all sense experience

  • as an unreliable source of knowledge.

  • But Locke didn’t go that far. Instead, in order to figure out whether the senses accurately

  • reflect the outside world, he introduced a distinction between what he called the primary

  • and secondary qualities of all things.

  • Primary qualities are qualities that physical objects themselves have. Theyre not in

  • our minds, Locke argued -- theyre actually in the stuff. These primary qualities include

  • things like solidity -- the density, weight, and mass of an object. And also extension

  • -- the height, depth, and width that a certain thing has. He also included figure, or the

  • shape of an object, as well as mobility, which is thiswhether it’s stationary or in motion.

  • So primary qualities, Locke said, belong to the thing itself.

  • Take this apple. It weighs maybe 150 grams, is the size of my palm, roundish, but firm,

  • with the slightest bit of give, and right now it’s moving through the air.

  • Those are its primary qualities.

  • But it has secondary qualities, too.

  • And by Locke’s standards, they are not real. At least not in any objective, agreed-upon way.

  • Theyre just in our minds. But they get there through the primary qualities.

  • I’m talking about things like its color, taste, texture, smell, and sound.

  • The secondary qualities of this apple are its redness, and how it tastes and smells

  • and feels on my tongue and hand. Even how it sounds when I bite into it.

  • Locke believed that the distinction between primary and secondary qualities explained

  • the disagreements that we all have about our perceptions of the outside world.

  • Like, we could measure this apple in a bunch of ways and all agree on its primary qualities,

  • but its secondary qualities would no doubt lead to some disputes.

  • Like, is it really red? What kind of red exactly? Cardinal red? Or carmine red? It’s kind

  • of dark purple at the top -- or is it just like a dark pink?

  • What about the sound it made? Would I call that crunchy? Or crispy? Or...bite-y? It’s like, apple sound.

  • We could argue about that kind of stuff til the cows came home.

  • But if we disagree about its primary qualitiesone of us is simply wrong. Because primary

  • qualities have nothing to do with you, or me. Instead they have everything to do with the object itself.

  • Locke’s reasoning was simple, even elegant, extracting a lot of explanatory power out

  • of very few basic concepts. As a result, it resonated with a lot people.

  • And one person it resonated strongly with was the Irish philosopher George Berkeley.

  • He was moved by Locke’s empiricism and took it seriously -- so seriously, in fact, that

  • ended up using Locke’s own logic against him.

  • He basically took empiricism to its logical conclusion, dismantling the whole process

  • of perception to the point that he had to wonder whether anything existed at all.

  • Berkeley began by taking apart the distinction that Locke made between primary and secondary qualities.

  • Like, think about this apple again. How do you know its shape?

  • Locke said that the apple’s shape, as a primary quality, is immediately perceivable.

  • But Berkeley pointed out that you don’t perceive some qualities of an object, while

  • totally disregarding others. Like, you can’t detect an apple’s shape without first --

  • or at least without also -- detecting its color. When you think about it, you can’t detect

  • any of the primary qualities without also considering the secondary ones.

  • You can’t see a colorless apple. You can’t feel a textureless apple.

  • In fact, if you try to strip away the apple’s secondary qualities in an effort to get at

  • the primary ones, you end up with no apple at all.

  • Try it: Close your eyes and imagine an apple made of only primary qualities -- so, it has

  • a certain shape and a certain size, but it doesn’t have any color or texture or taste.

  • You can’t do it.

  • You try to imagine it with no color, but really, youre probably imagining one that’s either

  • black or white or transparent -- the color of what’s behind it.

  • And if you try to imagine it as having no texture, youll find there’s still a texture

  • thereit’s just smooth.

  • Remember: Locke asserted that secondary qualities are not objectively real. They can only be

  • subjectively perceived. But now, Berkeley has shown that the two are inextricably linked

  • you can’t have one without the other.

  • Which means that primary qualities can’t be real, either. They, too, are just what

  • your mind makes of things.

  • So this led Berkeley to a startling conclusion: There’s just no such thing as matter.

  • There can’t be! Instead, there’s only perceptions.

  • Berkeley’s famous assertion -- his version of cogito ergo sum --

  • was esse est percepi: “to be is to be perceived.”

  • In his opinion, there are no objects, only perceiversand even then, the perceivers

  • themselves don’t really have any physical form. Theyre just disembodied minds perceiving

  • things that aren’t really there.

  • A little bit terrifying when you start thinking about it.

  • In Berkeley’s scenario, were all set adrift in a world of nothing but thought.

  • What’s scary about it is this, if everything’s just perception, then when the perception

  • goes away, there can’t be anything left.

  • So like, please, for the love of Pete, do not turn away from your computer! If you stop

  • perceiving me, I stop existing!

  • But, what if maybe you don’t care about me? Still, you’d better not go to sleep,

  • because as soon as you do, youll cease to exist! Because, you won’t be able to

  • perceive yourself! The only guarantee that youll continue to exist in your sleep is

  • to have a friend watch you when youre sleeping. Which probably is a non-starter, for a number of reasons.

  • But in any case, the second your friend blinks, youre gone!

  • So in the end, Berkeley believed there was only one thing that kept us --

  • and everything else -- from disappearing into oblivion.

  • God. Berkeley believed that God was the Ultimate Perceiver.

  • God is always watching, with unblinking perception that holds objects in existence even when were not paying attention.

  • The tough thing about Berkeley is, we all pretty much think he has to be wrong.

  • Very few of us are willing to give up our belief in the physical worldno matter who’s watching.

  • We are sensory animals! We really need this apple to exist.

  • Next time, were going to take a side journey into the world of knowledge. And then, in

  • episode 8, well see if Karl Popper can manage to get the physical world back for us.

  • Today we have learned about empiricism as a response to skepticism. We talked about

  • John Locke and his distinction between primary and secondary qualities. And weve seen

  • why George Berkeley thinks that distinction ultimately falls apart -- leaving us with

  • literally nothing but our minds, ideas, and perceptions.

  • This episode of Crash Course Philosophy is made possible by Squarespace. Squarespace

  • is a way to create a website, blog or online store for you and your ideas. Squarespace

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  • Crash Course Philosophy is produced in association with PBS Digital Studios. You can head over

  • to their channel to check out some amazing shows like Idea Channel, The Art Assignment, and Gross Science

  • This episode of Crash Course was filmed in the Doctor Cheryl C. Kinney Crash Course Studio

  • with the help of these awesome people and our equally fantastic graphics team is Thought Cafe.

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ロック、バークレー、経験主義。クラッシュコース哲学#6 (Locke, Berkeley, & Empiricism: Crash Course Philosophy #6)

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    羅紹桀 に公開 2021 年 01 月 14 日
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