Critical Thinking: Deductive and Inductive Arguments 3

so you notice that I have some generic argument forms on the board and the reason that I have those up there today and you can you can frame these in different ways the reason I've got them up there today is that we're going to look at some argument forms then we're mainly interested in the idea yes I want to sort of walk you through that concept and we're going to deal with a lot of examples your fork unlike a lot of critical thinking books your book does not stress this a lot but I think that when it comes to figuring out what kind of art you're dealing with its deductive or inductive this can be very helpful so if P then Q P and then Q this is sort of an abbreviated way of saying if P is the case P is some sort of claim so P could be my jacket is on the table it could be McDonald's coffee tastes better than the Burger King coffee that could be the world will happen tomorrow it could be the Packers won Super Bowl or it could be a false back Steelers what a super cool anything we want to be P this is sort of like algebra remember back in algebra variables same thing in arguments the same sort of reasoning that you used in in big mathematics and thinking about this gets used in language that's why you know your math scores on the SAT are not just testing company man they're testing can you work with symbols so he is a symbol he can stand for anything we want Q can stand for anything we want as well all of these letters can stand for any item that we want to put in there so if P then Q it's saying if P is the case Q is the case and it says P is the case and this is one of those those times when you know the conclusion ought to follow but in normal conversation what often happens we say look if you break the rules you're going to be punished you broke the rules then we wait and wait and wait and then finally the person says so I'm going to be punished exactly that's a logical deduction this is this is a old of our diamond form it's so old that it actually has a last name modus ponens which which you don't need to know if it is class but you know it's kind of interesting trivia anytime that you have an argument that's set up like this it's going to be a valid argument last class we talked about the difference between being valid and the difference being valid and invalid or being strong I'm sorry sound or Unseld if an argument is valid that means that if those premises are true that conclusion has to follow and it doesn't matter notice because of the structure now we're actually seeing in structure because of the structure of this it doesn't matter what you put in there it could be the craziest most outlandish unbelievable claim you want if you've got this structure and you accept these premises that conclusion follows so what would be some crazy claims things you couldn't possibly leave well something about FSU there should be a lot of things you wouldn't possibly release about ethnicity in the top college the North Carolina FSU is the top college in North Carolina I actually heard somebody yesterday jokingly referred as to Harvard on the murchison and you know that's not the case I think that's Hospital of the public schools the top school would be our flagship school right Chapel Hill do it for most programs I don't know about before to include that the private schools I don't know most Carolina that well so FSU is the top school in North Carolina and what's another thing you know what are they give you free tuition and that's you guys free tuition for Alston so if FSU is the top school in North Carolina then they get free tuition all of their students now actually so something that's not the case that they are the top scible if that's really the case well then they're going to give free tuition that's a valid argument it's not a sound argument because the premises are false right but here we're not worried about whether the premises are true or false we're worried about the structured form of the argument and this is a good argument for you can put anything you like in there can be about George Washington could be about you or your dog you know if your dog is what's a bad sign through the dog if your dog's nose I this mixed up it's hot and dry is that supposed to them then your dog is sick your dog's nose it's hot and dry your dog is sick you can do it with balls oh yeah if you give the dog chocolate you're gonna kill the dog you just gave the dark chocolate your dog is gonna die none of you know these are not your plants a lot of dogs can't eat chocolate doesn't do just fine but you see the general I guess this is an argument for this is always valid and it's always deducted so you know a lot just by looking at the structure of the argument now what you have to be able to do when you're in real life do you get arguments or somebody says well if P then Q P and therefore Q my point is proven no they've got arguments that you have to be sort of see-through this is the skeleton you have to be able to develop the skills to see through all the flesh and see the skeleton underneath you figure out what kind of animal you're dealing with these are both premises and this is the conclusion when we draw this line that means that we're separating premises from if P then Q is a promise P is a promise Q is the conclusion if we wanted to do we could put P Q if P then Q it's not what they are but where they are that determines whether they're on the sees our conclusions so if you look at this one this is a somewhat different this is about how to group things if you say a you know a being any single thing you want like you know that that camera up in the corner okay say is watching us but I isn't actually working a is a be that thing up in the corner is a camera all these are see you're saying that anything that's in the group B is included in a larger group C so all cameras are things that watch us therefore that thing up in the corner is something watching us right it doesn't matter what you put in there this is going to be a valid argument may not be a sounder if their camera is not working you know maybe it's not a or you might not even be a camera but could just be a dummy out there I wouldn't surprise me in that fester you know save a little money they do that in convenience stores too by the way they have know sometimes you see the camera off of the corner of the red light blinking all there isn't inside there's a red light that blinks sometimes a motor to make it go back and forth yeah what's happening yeah so so you know appearances could be deceiving but is not deceiving as if these premises whatever you want to put in these premises if those premises are true that conclusion he has to follow so once you accept these this goes these are both valid argument forms because of the form right this is why it's like mathematics two plus two always equals four right or if two things are equal to each other they're equal if two things are equal to a third thing they're equal to each other that always goes it doesn't matter what you put in there this is like mathematics in that way this is very powerful so if you if you learn these already two forms and you practice them so that can actually see them in real life arguments that's going to be very useful for you I'm not going to actually require you to be able to identify every single argument form although I gave you a handout that has a lot of arguments on it but I want you to be able to recognize them well enough so that you can tell at least is something deductive or inductive these are deductive because they're saying if those premises are true that conclusion has to follow if you look at this this is actually an inductive argument this is the argument from example this is a kind of they had argument that we make quite frequently as is is a P a is in the group a s property acts all peas have property X so we go from one member of the group or one member of the class to generalizing about the entire group this is a walking tall argument from example it's not a good form of marketing this is not deducted this is this is actually inductive because we're generally not asserting the conclusion with conclusive force we're saying it's probably the case that all peas have a property X but does that really hold up no let's put in some business let's put in some some material so this iPhone this is a this object right here is an iPhone and it also is the property of being dropped very often that's why I've got this case because I'm clumsy with it and I didn't want to break forever there's always the SIM cards I was popping out and have to reset it so my fiancee got me a nice powder box supposed to be almost indestructible and I have tested them you know not not deliberately but I've dropped it 15 feet on the concrete you know I've accidentally smashed it into things that's pretty durable so now we're saying this thing right here it is an iPhone and this iPhone us the property being dropped therefore most iPhones get dropped a lot really no this is the way in which we lead ourselves astray but no or other people need us astray or we lead demonstrates we're trying to manipulate them a lot of advertisements work like this don't they they present you a case how many of you watch the Super Bowl last night at least watch the ads okay so most of you think about what the advertisements will often do they tell a story and they show a case and in that case either something really good happens or something really bad happens and if it's really good then good exactly well make up a name for us for us is an average person Horus want that product and is very happy therefore it really anybody who buys that product is going to be very happy you know it depends on a lot of other things doesn't this is not a strong inductive argument this is a weak inductive argument the other way that arguments work and we're going to spend some time later on it's not this class session but in a few weeks looking at a lot of the advertisements in st. Holly work either the claim is along the lines of something good happens they're free to buy our product or if you don't buy our product what something bad happens I definitely does you know this person watched everything that could have been prevented with Nick whatever product you like I definitely like somebody say hey what's that life on yeah there you go and the way advertisements often work is by using argument from example argument from example from a critical thinking perspective is not a strong form of organization when you're carrying out inductive arguments you want to have better ways of now those are some these are some valid arguments that's a fairly bad or weak inductive argument let me give you some invalid arguments we'll look at some of those for examples so if you think there's a common mistake that gets made and this is often termed within a fairly long language the affirming the consequent that requires you to know a little bit of technical vocabulary that I'm not going to presume you know this is actually that what we call the antecedent cuz it comes first the consequent what I'm more interested in you seeing is the connection between these if I say isn't P then Q and Q is the case therefore P is the case I see some of you shaking your heads already so you're getting sometimes what it takes is to substitute some some material in there and then you can see how it doesn't follow so let's say we take the old standby yeah so this MVP yeah it snows and they adult classes are canceled right so this is P this is Q so the Fayetteville put that down here at the bottom into snow and we're going to put here what's going to be cute last or canceled so this is this really a good argument if these premises are true does that conclusion have to follow could you think of a case where these are true if this doesn't well move in with an examining perfect yeah because this is pretty much true then we're going to talk in a moment about quite a go from deductive to inductive classes can be cancelled it could be for a holiday maybe there's a what's up a hurricane yeah it could be what's that bomb perhaps yeah don't anybody call it in because they this would be a very bad place to do that because I don't know if you realize this but you know we're so close to Fort Bragg that a lot of monitoring of cell phone traffic takes place you may not even you may not even know when you're being listened in this was actually one of the safest places you could be you know these are the it bombs right our terrorist attack because there's there's so much so much resources devoted to making sure that one doesn't happen here it's all behind the scenes yes if you look at this no notice here's the here's the skeleton here's the flash on it sometimes seeing that the flesh can help you pick out the form of the scholars and have you ever been in drawing classes so you know that's the case right sometimes being able to see the form will help you put together if you wanted to make a bad argument to fool somebody you could actually take this and use it as your mom and then just start putting things in there and they might be taken in because people do often by hiding what about this one phase of being remember the one about professors and terrorists let's do the say dr. Sandler and ways this thing about diligent in his work and all terrorists are diligent in their work therefore I understand there is a terrace now it doesn't have to be terrorists diligent in their work it could be this banana is a very you know tasty fruit all oranges are tasty fruits therefore this bananas and orange you notice again premises can be true and the conclusion won't follow frozen and if you want to figure out whether this is valid or invalid you might do that just by substituting things in substituting what we call content if there's also other techniques that you can use they text what have we don't get to cover in this class for determining whether these are valid or and yes when you to prove it to yourself what do you mean by dr. Sattler a and B yeah these just any sort of class right any sort of group this this will take some wrapping your head around we're not in memorize 20 last time about the the habits of thinking that you have to sort of shift yourself out of if you want to make use of this then it requires quite often developing new habits because we used to do things like this in grammar school we don't do it anymore so a lot of people have been set behind you might say this used to be a sir there's part of the course and there's certain mental habits that are developed by working with argument forms by working with mathematics by working with logic develop certain parts of your your mind to higher-level to be more FAFSA to be ready to see things and then just populate with them like that and if you haven't done it then you know this is one of those sort of things where it's going to take a bit more work again in this class I'm not going to require you to identify argument forms and pick them out and tell me this is you know affirming the consequent and I'm going to ask you to tell me whether the Valor in doubt I I'm you know happy if you could actually tell me is this a deductive argument or an inductive argument this is that's why I gave you this list of forms now there's some other inductive ones but let me talk for a moment how you could turn deductive arguments into in-depth inversions think again what are some of the words that you associate with inductive arguments likely very good usually probably the most yeah then we're going to use most in here likely probably usually you could use any of those in here and so you may see some things that look like some of these deductive argument forms but they may have that language so if P then Q let's say we take the first one that let's say we change it from this which is you know absolute and lightly or usually or generally right and then we say P is in fact the case therefore what are some things that you feel fairly certain about that have some exceptions you know think about the dog nose again the dog's nose is - and dry the dog is probably sick where you get a dog that has a hot dry nose you know maybe some dogs do I don't know I'm not a veterinarian or you know biologist or anything like that if you publish PC do you think that a person could safely consume one sitting we're gonna live eight slices okay and you mean like big slice not like you know yeah not that you bring home a pizza from Walmart and you cook it then he cut into 12 slices that are great thin okay so yeah 12 big pizza eight slices if you eat more than eight slices of pizza you'll probably be sick no but so you tell some kid that you know I see you eyeing the pizza if you eat all sleep Pauline slices that pizza then you get that nice slice you're probably gonna be sick and they go ahead and do it you know then they get sick you say well look I spelled it out pretty you chose to do that then you're not asserting that if these prophecies are true that conclusion absolutely follows right because you're using the word probably that makes this into an argument now notice it has a form it has a construction so did you see an argument that's set up like that no matter what the P is are there the Q is you should be telling your son ha ha that's an inductive argument think about the advertisements for antidepressants posted a to advertise there's a lot of side effects antidepressants there's some other psychoactive drugs that they they sell on the market now what do they say most people experience most people who are suffering from depression experienced some relief if they take Zoloft okay that's one of the little cloud that bounces in think okay well we'll get to the summary minute so most people experience some degree of relief so if you are suffering from depression and he takes a lot you will probably feel better you do take it you'll probably feel better doesn't say we will all automatically you might be in that you know whatever it is 10% 15% it doesn't feel better now notice that the work probably is going to be in there likely if it's going to be a strong inductive argument if you're just shooting for a week inductive argument then you could say some or possibly or maybe and that's what they do the sign of taxes and then they start talking very very fast side effects may include a little of you know you look at if it's all very fine print and there's about 30 different things your ears might fall off your toes might like curl lobs you may die but you know that's not likely they're not they're not using this sort of structure of argument with that and they're now asserting that you are likely to be in that case that's what I mean by side of things when the side effects become really likely then they take it off the market usually right only minimal errors are those class action lawsuit Orioles yeah if you were affected by such and such you may be entitled to yeah there be using the word may in that case there because of lawyers there they're hedging their bets they're not actually meaning they than their meeting most likely you're most likely entitled so that's why you should contact us very using may also because what will ultimately decide whether you're entitled to know how the lawsuit turns out so they don't want to they don't want to say you are absolutely going to get along you know thousand dollar check because what happens if they lose the suit they would be on the hook for a thousand thousand dollars over that so they're they're smarter let's look at a few more ways of turning deductive arguments of denied Americas another example is one that I haven't put up before an old standby which all RC therefore what do you think the conclusion of all I see very good and all of your friends who smoke cigarettes Clough a lot people who Quaffle ox what's that well we've already got all people who smoke cigarettes coffee lot so if we have a we start putting things in here he has to stay the same and now we need something new for the speech so well something let's I know this isn't true because actually I should be with one of these people I used to smoke and place to be able to run 2 miles in under 11 minutes when I was in the area we would actually go on 5 mile runs and we would we were young we've gone 5 mile runs every day and those of us who are smokers would smoke while we were running pass a cigarette up and down the line but let's just assume that these signatures so all of your friends are people who smoke or an all of them all of them for the next round all good friends who smoke quaff a lot all people who walk a lot can't run very well therefore all of your friends who smoke not very well if those premises are true the conclusion does follow now you know these these are not actually premises that you should believe them all of your friends who smoke quaff a lot let's leave that one there but all people who thought well let's change that to most people and we give a conclusion to most people most of your friends are small don't run very now we're not dealing with a deductive argument anymore this does have a certain form though and you could put whatever you want in there it could be all of your relatives are good cooks most people who are good cooks make good spouses therefore most of your relatives make good spouses it could be that you know some people who cook well don't make good spouses because they beat their spouses with the frying pans like that right where they they you know deliberately cook food that their spouse doesn't like to show off their culinary skills who knows the point being this they all have the same structure this structure makes rich strong inductive argument so whenever you see something that has this structure if those premises are true then you're making the assumption that that conclusion probably follows doesn't there's some other examples forms particular forms for different kinds of inductive arguments that I just want to clue you into we're not going to talk about them in waffle off today but later out of the semester we'll come to them what is the argument from analogy already say something property to you could be you like it or you don't like them because a lot of your decisions or your inferences about what kind of foods that you would like to to eat or not need or what kind of music you would like to listen to or not listening to or what kind of shows you'd like to watch or not watch are based on analogy because as a matter of fact websites have gotten very sophisticated about this when we look at an analogy later on we're going to look at some examples of how to use an analogy and if you use the Pandora radio station thing the Navy is oh well Hulu and if you've subscribed and then and then rate shows if you like this then you'll probably like this what are they basing that they're saying some things have properties in common think about pizza what water keeps us character is that anybody in here who doesn't like pizza okay sometimes I have a class where one person doesn't like pizza what do you like about pizza I'm not asking what ingredients do what do you like about these if you had to tell somebody okay it's convenient what makes it tasty there's a combination of certain elements Joey yeah the pizza combines crispy and soft and you know the tomato anything with the meat or the vegetables and a lot of combinations you can do so Pizza has a combination of tastes it's convenient can you think of any other reasons why you like to eat some of these a lot of people okay good so it has properties XYZ it's convenient it was a good combination to taste a lot of people and you like it that's property - do you think of any other dishes that might meet that requirement spaghetti okay spaghetti also has the properties of being convenient feeds a lot of people especially making a lot of you know spaghetti make a big top of it and it is a combination of tastes too distant more if you put meatballs in it or you know you put Parmesan cheese on top things like that problem number one property qo so that you know like yeah so you can probably infer that if you like pizza for these reasons and spaghetti also has these reasons you're probably going to like spaghetti yeah you can also do this with things that you don't like things that you don't like have these properties this thing has these properties think about people there's some traits that drive you nuts by now you should have you you probably you know have enough experience you could put together a list of properties I actually did that at one time when I found myself in in multiple relationships where I kept making the same mistakes there's a comedian who actually has a good joke about this he says something along the lines if your relationships keep breaking down and it keeps happening it keeps happening for the same reasons it might be you that the problem is actually you and there's a truth that what would it be you're doing the wrong kind of inferences about people in that case because when you pick somebody to go out on a date a date with you've engaged in an argument you've actually said you've come to the conclusion yes I should go out with this person you have some sort of reason for doing them and you could give those reasons and your friends may argue with you about those reasons right or your family well you can do the same things the same sort of structure of analogy with who you should go out with Lucia danger signs when when somebody is crazy or dangerous in other news so let's go had these properties this person also has these properties and so from so which we make them do something bad they killed their mom okay so let's go ahead these properties and kill their mom they constantly argued with their mom and secretive around the house yeah I mean you're more than likely to live in a moment so let me get this straight the the research is showing that if the pop up that is connected to the home said that you're on you're more likely to look at it and then more likely to click on I think that's how we have to change it right that could be I know that when it comes to most websites now there's so much profile information stored about you on your either on your computer or a lot of sites that you have profiles are like Facebook for example when I when I put that I was single I started Facebook when I was in the process of getting a divorce and so Facebook doesn't he have a divorce he has single interrelationship it's complicated married and get is just so it doesn't have disengagement so when I went from married to signal suddenly all these answer to popping up all the time they you know women in their area and they were and they were you know pretty funny some of them because I didn't get on forty years old so they would be like you know fine forty you're limiting their area who are I have kids and Facebook knows it's that would say you know find single moms in your area then one of the best things about putting I'm engaged on Facebook no more they'll dance now other things about you know find out how philosophy professors can make a hundred grand to hear because then you click on it and turns out to be complete bogus free trips for professors and then you find out yeah free trip if we get a little students what all that is based on the logic of analogy if you like this

Channel: Fayetteville State University

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Length: 39min 57sec (2397 seconds)

Published: Mon Feb 07 2011