okay so we're going to continue our discussion of knowledge here and as we saw Dart really kind of um started everybody on this skepticism path again but you know really uh around that time there were other people who didn't agree with deart there were the empiricists like John Lock who rejected this strict about knowledge and he and the other people who ended up being called empiricist decided that look really knowledge begins with perception and sensation that's where we get a lot of our information probably most of our information really um but he broke it down um John Lock anyway broke it down into three kinds of knowledge he had this idea that we had intuitive knowledge and that that was things that we know just by the meanings of the words so if we understand what a square is we know that it's not a circle so the proposition proposition a square is not a circle is known pretty much just intuitively right then there's demonstrative knowledge which in some ways can come from intuitive knowledge depending on what it is uh something like the Pythagorean theorem can come out of our knowledge of what a triangle is we can say that if we understand that a triangle the angles um you know have these certain properties that they have to have in order for it to be a triangle we can figure out what the Pythagorean theorem is and then sort of separately there is the sensitive knowledge which is known through our perceptions so we can say that we know that there's a cat on the mat because we perceive that cat so it's fairly simple there and we know what a cat is maybe that perhaps is intuitive knowledge maybe that's learned by Sensations as well so these he was really interested in things like justice and you know kind of like Plato um but he thought that we come to ideas of justice and things like that through our perceptual uh observations of the world so we go out and we see what people do and what works what doesn't what makes goodness for humans and what doesn't and then we form an idea of justice so the idea is that we go out there and experience the world and then that's how we get a lot of our knowledge that's not perhaps just intuitive knowledge and these um kinds of knowledge for him of course can be combined as we already already kind of saw with the whole idea of the pan theorem anyway then there was David Hume who had a different kind of skepticism than LA or than uh dayart instead of questioning so much our Perceptions in general he doubted things like our assumptions about cause and effect so he said that look we might think that um us dropping something causes it to fall but do we really know that we can observe that when we drop something it falls but we don't really have a lot of evidence according to him about what the cause of that what the cause and effect might be we can we can have correlation ideas but to extrapolate cause and effect from those he thought was perhaps going too far so he had a different kind of skepticism in the same kind of way he questions our assumptions that a self endures over time because he says look if you look inside yourself all you really going to see is you are self-inking about stuff you're not going to see a quote self and we'll get to that perhaps a bit later but um he he also challenged Arguments for the existence of God and claims of religious Miracles because he thought that he was very conservative in a sense about what knowledge is and what we should believe and he thought that religious Miracles went too far outside of our normal experience for us to accept them so um on the other hand though he didn't believe in global skepticism so he didn't really think that we should doubt everything he thought that was kind of a bit much and that we really couldn't live that way so he was more judicious about what to doubt perhaps than something like the evil demon of dayart that dayart might be suggesting with the idea of the evil demon so when we get into the 20th century views of knowledge we kind of end up going backwards a bit to Plato as we said earlier who thought that knowledge is really something like Justified true belief so um what is truth you might ask in this case usually philosophers are talking about the something like a propositional truth so a proposition is true if it only if it corresponds to the way the world is you can think of a proposition as the content of a sentence just for simplicity's sake so uh a proposition that is snowing you know can be expressed by the the sentence that is knowing or by the sentence that in in a different language right so you could express it in a different language you could express it in sign language but the proposition the content of that sentence is going to be the same so if it's really Tuesday then according to the prop correspondence theory of Truth the the sentence or the content of the sentence it is Tuesday is true so we'll just take that first of Truth for now and say that this is the classical analysis of knowledge that most 20th century philosophers adhere to at least until the next slide um so s who is a person knows that p a proposition if and only if the proposition is true the person believes that P and the person is Justified in believing that P and then we get into what justif a means and that causes a whole lot of problems and even if we could solve that problem the problem of justification geder published a paper that made everybody rethink this whole idea of Justified true belief which seems kind of reasonable right if you want to talk about knowledge it makes sense to say that somebody has to know it that it has to be true and that they have to be some kind of way Justified but then gar said well G didn't use this example but this is an example that people use and call a g example because it's a little bit simpler than the example that gett used so suppose somebody walks by a stopped clock that reads 12:00 p.m. and the person forms a correct belief that is in fact 12:00 p.m. then their belief is Justified right it's Justified because normally we would say that it's reasonable to form a belief on the looking at about the time by looking at a clock okay so their belief is Justified and it's also true right because it was 12:00 p.m. when they walked by the clock clock says 12:00 p.m. but supposed the clock was actually stopped at 12:00 p.m. and they just happen to walk by at that moment when it was 12:00 p.m. do they know that it's 12:00 p.m. and it seems like the problem is that they could have easily wrong if they had walked by 1201 they would have um they would have formed a false belief right because they would have looked at the clock it still said 12 but it would actually be 12:01 so it seems to be just chance that they walked by at 12:00 p.m. when the clock happened to be correct does that mean since they have Justified true belief but don't seem to have knowledge does that mean that there's something missing in our account of knowledge as Justified true belief you can say well okay he had a false belief right he falsely believed that the clock was working but then we start asking okay is one false belief enough to stop a person from actually having knowledge and an example is a detective who thinks that all 12 Witnesses are telling the truth about who qu committed a crime when in fact one is lying does the false belief the detective has that all 12 Witnesses are telling the truth mean that the detective does not know who committed the crime and it seems like we don't want to say that right just because we always have some false beliefs we're never going to be perfect and you might want to say well it seems like the detective isn't essentially relying on this one line in the witness's testimony however it turns out to be really hard to explain what essentially relying on a belief means you can try to come up with examples and it's pretty easy to come up with examples where there are false beliefs involved that may be essentially relied on or may not be and people have tried to sort of tweak this whole Theory and come up with a way to say well you know um they can be you can have a false belief that you're not relying on or that you are relying on and we can somehow tell the difference it turns out to actually be pretty difficult so we'll see next time where we can go with this idea and whether we can fix it