Theory of Knowledge: Three Responses to Skepticism

my name is Jennifer Nagel I teach philosophy at the University of Toronto and today I want to talk to you about three ways philosophers have tried to solve the problem of skepticism the Cartesian way the Rosselli in way and the Mauryan way the Cartesian way comes to us from Rene Descartes meditations published in 1641 you'll recall from the last video that Descartes dramatizes the skeptical problem with a scenario involving you and an evil genius who is determined to send you all kinds of misleading impressions after stirring up maximal doubt dick Hart asks whether there is anything you can know for sure what about your own existence hey it looks like the evil genius couldn't possibly deceive you about that for him to deceive you about anything you have to exist as long as you're thinking about anything you can know for sure that you exist as a thinking being it's not easy to leverage this one item of knowledge into a larger solution to the skeptical problem but Descartes notices there's one more thing he has at his disposal as a thinking being whether or not he's being deceived he's aware of a great diversity of ideas within his mind although at this point he's not yet sure whether these ideas represent anything real he observes that some of his ideas represent greater and lesser things and his greatest idea of all is his idea of an infinite and perfect being that's an amazing idea in fact it's so amazing Descartes thinks that it couldn't come from an imperfect being the only possible source for such a great idea is an infinite and perfect God so God they for exists now if the universe is run by a good and all-powerful god Descartes argues we can't be trapped in an endless dream of unreality or left in the clutches of an evil demon who deceives us all the time when we think carefully Descartes maintains will see that the skeptics global bad case is not really possible an evil demon can't possibly exist in a world with God and we can prove this God clearly plays a very important role in the Cartesian response to skepticism and from the start critics have raised worries about de cartes way of trying to prove the existence of God in particular it's not obvious that he's on safe ground as he reasons about the sources of his ideas if he's still at that point supposed to be taking very seriously the idea that there could be an evil genius distorting what seems true to him but whether or not you like the Cartesian strategy you might wonder whether meaningful responses to skepticism have to take the very ambitious step of trying to show that the skeptics bad case is flat-out impossible a different strategy would be to allow that the bad case is possible but then argue that we still have very good reasons to think it isn't actually real this is Bertrand Russell's strategy unlike Descartes Russell thinks you can never have an airtight logical proof that anything is real beyond yourself and your experiences and in particular it's logically possible that your entire life is a dream however Russell argues we have no good reason to accept the hypothesis that were dreaming and two good reasons at least two good reasons to accept the common-sense hypothesis that our experiences come from ordinary physical objects first the common-sense view is simpler Russell says it's the best explanation of the regular patterns in our experience second common-sense is our starting point the existence of the outer world is one of the instinctive beliefs on which all knowledge is ultimately based according to Russell were only entitled to reject an instinctive belief when we discover it's inconsistent with other instinctive beliefs but our belief in the outer world isn't like that if we believe in a real outer world we can come up with a perfectly consistent scientific story about how perceptual experience generally works and even about how dreams are ordinarily caused Russell thinks that the sceptical argument is powerful enough that we should feel a slight element of doubt in any judgment we make about the outer world but he also thinks that our reasonable judgments are still strong enough even with that shadow of doubt to count as knowledge skepticism is a remote hypothetical possibility the doesn't bar us from gaining knowledge through ordinary sense perception or more systematically through science some critics of the Roselia response to skepticism have wondered whether he's entitled to say that the existence of the outer world is the simplest explanation of our experience after all there's something simple about saying that all experiences come from one evil genius rather than from millions of outer objects other critics have wondered whether it makes sense to talk about having knowledge while keeping a shadow of doubt in the picture even if Russell makes the case that it's simple and reasonable to have common-sense beliefs it's not entirely clear that he's given an adequate defense of the notion that these reasonable beliefs should count as knowledge if you're looking for a response to skepticism that sweeps away doubt you may prefer the Mauryan approach GE Moore doesn't think you have to prove that God in order to know that there's an outer world and he doesn't even think you have to reflect on the ways in which the outer world provides a good explanation of your experience if you want to prove that the outer world is real just look at your hands or your legs or any objects around you here is one hand and here is another hands our external objects therefore external objects are real if the skeptic suggests you don't really know that your hands are there in front of you Moore says you should fight back by accusing him of being ridiculous and you should brush off his demands for proof sometimes you can know things like the fact that you have hands without being able to prove them similarly you can just know that you aren't dreaming right now even if you can't prove it something odd about Moore is that he says you can prove that the external world is real while also saying you can't generally prove that your hands are real but notice that the claim about the external world is the kind of general theoretical claim that philosophers make and the claim about your hands is a very basic fact about particular ordinary things the fact that there's a hand in front of you right now is so basic it's hard to think of anything more basic you could point to as a reason to believe it if the skeptic tries to undermine common-sense everyday knowledge with some fancy philosophical argument you should have doubts about that argument and not about basic common sense so Moore actually agrees with the skeptic that if you were in the bad case dreaming in a bath then you wouldn't know there's a hand in front of you but he points out that this is a big if more things your common sense knowledge would only be in trouble if you were actually in the bad case and the skeptic hasn't proved that you are the flipside is that if you really do know there's a hand in front of you then you know you're not in the bad case the outcome of the battle between Moore and the skeptic depends on your starting point if you start with common sense Moore looks pretty good but even if you like the strategy of being stubborn in the face of skepticism and clinging to common sense you might wonder about why skepticism ever felt appealing and you might wonder whether the skeptic is making some mistake that we could diagnose or whether skepticism might even be self undermining the next video in this series explores these questions by looking at three more contemporary ways of trying to solve the problem of skepticism you