1.1 Basic Concepts: Arguments, Premises, & Conclusions

hi welcome to an introduction to logic this is a video series that introduces introduces students to the basic concepts in logic and in particular we're looking at categorical propositional and predicate logic although you don't need a textbook to watch the videos we are following a textbook and we're using the textbook concise introduction to logic by Patrick Hurley we're using the 11th edition this is one of the most widely used textbooks for logic within the country and so I think a lot of people will find this video helpful these this textbook is frequently used of course in undergraduate courses we're going to look at a lot of different concepts throughout this video series there's actually 40 different videos but in this first one we're just looking at really the basic of basic concepts we're looking at arguments premises and conclusions and and we're going to be following along with the Patrick Hurley's discussion of that same thing though you'll see that I don't necessarily agree with everything early says or at least I don't put it the same way early does but it's a great textbook nonetheless let's just start off with a real basic question here which I think sort of deserves some discussion right from the outset before we sort of get into what arguments premises and conclusions are and let's start with this question what exactly is logic right yummmm you may have if you've never taken a logic course before I'm sorry for the term logic I'm you know of course Captain Spock and Star Trek he talks about logic what exactly is logic I think there's a great even though logic goes back all the way to the ancient world with the writings of Aristotle and even plato logic is I think the best example or best sort of quick phrase about what logic is comes from a philosopher by the name of John Locke many of you may in government or even your introduction to philosophy courses may have heard of John Locke John Locke was a modern philosopher and he said logic is the anatomy of thinking of human thought and I think that's a great way of thinking about what logic is so we're going to give this answer logic is the study of the anatomy of thinking and for all of you watch not there I'm sorry my handwriting isn't always the best but it's the anatomy of thinking and I think that's a great way to think about it because what exactly is anatomy anatomy is the study of the different um is a is a is a subset of biology and what it Anatomy does is in at any studies the different organs within a body and how those organs function together and in many ways that's what logic is even though we can't see them there's certain organs or at least there's certain yeah there's certain organs in our minds that allow us to think in certain ways and to think correctly and this is an important distinction there is a difference between correct reasoning and incorrect reasoning whoops this is an ugly guy correct regime versus incorrect reasoning what exactly counts as correct reasoning well two reason first and foremost blurs lots of different things we do when we think we can imagine right and this sort of thing but we'll see that it's a sort of thinking that logic is concerned with is the form of reasoning that's contained in its reasoning oops for some reason in argumentation and in fact we'll see that what logicians study essentially are the forms or rather the structures of reasoning that allow us to make arguments now of course what exactly is an argument right we can keep asking this question what is an argument one argument is essentially it's composed of two different things first off an argument as always contains a premise at least one but usually multiple premises and the second thing that it contains is a conclusion the premise is supposed to support the conclusion right so you can think of the premise as the evidence that we give when we make claims and that's really to put it simple that's what I want you to think of as an argument argument is essentially when you make a claim you assert something is true right when you say that something is the case and you provide evidence for it that's in the most rudimentary sense what an argument is and we'll see that logic studies arguments and the most critical basic feature are the premises and the conclusions of our arguments okay one thing too we should make clear since this this is the first video let me open up quickly open up a new template here one of the things that I want to quickly reference here is the in logic there's logic there's different domains within logic right the first domain of logic the one we're going to be looking at is what we might call formal logic formal or symbolic logic and I'll talk about what that is in in a minute the other type of logic here generally speaking is informal logic and we'll see that the basic difference here is that formal logic seeks to analyze whether or not an argument is a good argument whether or not I can support its claims by analyzing the form that that argument takes whereas by contrast informal logic is concerned with the content of our thoughts so let me give an example here because that may sound fairly sort of obscure the difference here between form and content I want I want to give you a very classic argument that comes up goes all the way back to Aristotle and it contains three lines three statements the first standing here is that all men are mortal right Socrates is a man therefore and here just watch the video you'll know what comes next if all men are mortal and Socrates is men then therefore Socrates is what is it he's mortal right he's mortal and this is this is a standard form sort of syllogism actually we're going to use this term later on especially look at categorical logic but an argument that takes this shape this is known as a syllogism okay all men are mortal Socrates man therefore Socrates is mortal now why is this interesting here because this argument we'll see is actually a valid argument which means that it's a good argument uses correct reasoning but guess what we can do we can take each one of these two things this is your premise this is a premise so there's two premises and then this is the conclusion down here okay but what's what's amazing actually is the logicians going all the back tears out aristotle discovered that these take a specific form what if we took you'll see that these have different words that sort of reappear over and over right Socrates and moral and these are what we call terms and what happens if we symbolize the terms with letters so let's do that now to rewrite this it looks like all em are T right and I'm going to slightly change it just to sort of make it a little clearer when you'll know why later on the other videos let's say all persons named Socrates are M men therefore all persons named Socrates are T for mortal you can see here this was our t this was our s this was our M okay so this is essentially what I've done is I symbolized this argument into its form right you can see I've stripped out the content we're not talk about men or mortality more we're just looking purely at the arranged of the terms and the reason that what's fascinating about this is that if I replace any any of these terms with something else totally different right something like all all plants are things that have cell walls right pine trees are things that are plants there are four pine trees are things that have cell of cell walls for instance if I can replace any one of these terms with other with different content in the argument though regardless of what words I use or what terms I use will always turn out to be logical this is um this is 100% of correct reasoning no matter what I'm talking about no matter what I'm talking about now of course you can see here this is so what is formal logic study formal logic basically takes all sorts of different arguments puts them into formal analysis and then we mainly just look at the forms and try to determine whether or not the reason is correct now let's go back up to here what about informal logic and what I'm talking about content what exactly does that mean well what if I gave a different example what if I took the form of the reasoning but I put in to the variables here terms that really aren't real that are not true for instance what if I wrote if I change the nu by saying that M is unicorns tier-one horned animals as here would be Suzy so it looks like this all unicorns are one horned animals all things name all persons all for animals identical to Suzy are unicorns therefore all things identical all animals identical to Suzy are one word animals see that argument uses the same form of reasoning it's correct in that sense but the content is the problem because since unicorns don't exist that means that I've made a logical mistake they're talking about things that aren't real okay so in formal reasoning and we'll talk about this formal reasoning is concerned with content to a certain degree the informal logic studies essentially the content and the ways in which we can arrange our our arguments and our premises that our evidence and the way we think in fact what this is there's a similar difference here though it's not identical between deductive reasoning which is usually associate here with formal logic but they don't mean the same thing and also inductive reasoning which is by definition actually informal logic so we're going to talk about that here in another video but I want to get you see this is essentially what logic is and logic provides us with an absolutely fabulous way of assessing arguments ultimately and you may not realize it but everywhere you go people are trying to convince you to believe things everywhere you go on YouTube your friends at your school at your church on television advertisements everywhere you go in fact perhaps maybe more than in any other time in history you're confronted with arguments you're confronted with with a rally you're confronted with claims right to believe people want you to believe things the fortunately the majority of the things that people ask you to believe actually use in correct reasoning there and that's what we call a fallacy a fallacy literally means a false argument right and so what we want to do is we want to assess the claims that we're confronted with in order to determine what we should actually believe and this is really really really important especially think about politics for instance politicians make lots of claims and they give reasons for their claims which means they're giving us arguments but we have to assess those to determine whether or not they're logical so logic this is effectively what logic studies okay so let's move down here and make another distinction here these are all claims right but these are not arguments right in order to fully understand arguments are we have to also look at what are what are not arguments right these are merely statements these are merely statements and you combine statements together to create arguments right and you can see here is the number of time I talk Allah truffles are loaded with calories melatonin helps relieve jetlag political candidates always tell the complete truth now we know that's out you're right no wives ever cheat other husbands that's not true Tiger Woods plays golf and Maria Sharapova plays tennis okay these are all statements but they're not arguments they're not arguments because they're just singular statements right in order to have an argument we have to combine multiple statements together right such that they become they relate right so we have some statements we're going to talk about as premises and some statements we're going to talk here about as conclusions what's the difference the conclusion is the claim you're supposed to believe and the premise e or the premises this is that it is that you're supposed to date you're supposed to base the claim off of right so you can see it works like this your premises and conclusions now one of the thing that's interesting is in ordinary arguments a lot of times the conclusions and the premises are mixed up we're going to you're going to see here that in logic we're going to abide by what's known as standard form notation which means that the premises are always going to come first right and the conclusion will always come last and in a standard form proposition we're always going to always have two premises and one conclusion but I think that is the subject of the video coming up here that's the first thing to think of by contrast I want you to notice that a lot of the sorts there's lots of different statements in the world that are that don't count so there's lots of different things that people can say that don't count as statements right because they don't actually claim anything for this if you ask a question if you propose something if you suggest if you tell someone to do something if you you know yell out fantastic the these are sentences well they're not even sentences let's say their utterances but they don't actually but there's no claim right so they don't count credit they are not going to they're not statement in the logical sense of the term right they're just purely utterances and so one of the things you need to do is you need to have to learn slowly they really just through powder to repetition learn to differentiate what matters when we because in an ordinary sort of conversation people are going to tell us a lot of different things they may combine they may have questions combined with evidence combined with suggestions and claims and one of the things we have to do to analyze arguments is we have to sort through and figure out what matters or what does it strictly speaking this stuff doesn't matter what matters what we really want to be worried about here are I'm sorry what you really want to be worried about here or whether or not it makes it claim it is the claim properly supported and it finally of course the subject of logic and it's more proper sense when we get to categorical or proposition or predicate logic is whether or not they're formally organized in a way that allows them to be correct forms of reasoning now here's two examples we can take of arguments two examples of arguments here's the first one all film stars are celebrities Haley Berry's a film star therefore Haley berry is a celebrity okay we can already see that the print this is the first premise this is the second premise and we would say this is the conclusion okay and even though this is really organized you can see this is organized not in perfect standard form but fairly close right you can see here the terms film stars celebrities Haley berry film star right those are the terms okay let's take a look at this one over here let me change the color my pen here first of all you can see there's terms this is some film stars are men Cameron Diaz is a film star therefore Cameron Diaz is a man now this is a good example right because this is actually organized correctly but you know this is you can see the difference here because this is not true right it's true that well that's actually sales this is the first premise this is the second premise and this is the conclusion now what's the difference here this is actually a correct form of reasoning if follows and by saying it's correct what we mean is that this argument in terms of its form is what we will call truth functional meaning and this is why I'll explain while this one's wrong and this one's correct right meaning that since it's organized in story of where these terms are in the specific order the way we looked at it earlier if since its organized correctly it means the truth functional meaning that if these first two premises are true then the conclusion will also be true necessarily it will always be like that if the premises are true the conclusion will be true now be careful here because if I have a false premise then the conclusion will turn out to be false right so yeah that's that's the content issue there right you have to make sure that film stars are celebrities and stuff like that now you can see here this may actually be a false premise all film stars or celebrities well I guess if you're a star by definition you are Solaris oh yeah I think it is out but what about this one this is some film stars or men notice the difference here at all some film stars are in Cameron Diaz is if those are there for Cameron Diaz is a man you can see or that this has a two privacy's in a conclusion but it uses a poor reasoning who will say this is a poor argument why is it poor well because here look at the premises this first premise is true some film stars are Cameron Diaz is a film star that's true she's not my favorite film star but she is a film star so the parentheses are true but look the conclusion here is false which means that this is not truth functional okay so an argument that good argument that has views correct for a reason is truth-functional you mean it's as if if you pour truth into the premises a conclusion will always spit out that's true whereas it in poor reasoning is when you pour truth in and falsehood comes out at least once right and unfortunately the grand majority of arguments probably that exists in the media today or maybe in the world are poor arguments there like this so our goal is to figure out for a reason how what sort of forms are truth-functional and then always argue like that and then of course we can use this as a tool to assess how other people are you so these are two different arguments now how are you supposed to figure out what the conclusion is I supposed to figure out what the conclusions the first thing you should do when you actually hear read or I guess you hear or read an argument is you should figure out what the conclusion is and I would say ask your a simple question ask this question what is the take away what does the person who's arguing whatever it is you're hearing right what is the take away what is the claim they want you to agree with and believe that's what the conclusion is going to be now usually most conclusions in because of the way human language proceeds we use words we're going to call these conclusion indicator words we use certain words that help us to recognize the conclusion the most typical you'll see is therefore where a website where for thus consequently we may infer accordingly we may conclude I mean the conclusions right there right it must be that for this reason so this is a very I'll circle the ones that are common so and therefore these are fairly whole it entails that hence it follows that right that's also known implies that as a result so one of the first thing is asks just for when you read it argue at first what's the take away and if you can't figure the take away number to search for the indicator term search for the indicator term right because even though this form of logic we thought we we're going to take arguments to explain an ordinary language formalize them analyze that but we have to figure out the occlusion is so you've got to look for that indicator term if you can't find an indicator term or you can always look for the premise indicator terms oftentimes the present the premise remember a premise are accounts as the reasons you the reasons you give for the claim right in the premise these words usually come right before the premise you say for these you say dogs are great animals since threat there's a protein in a care term since they've biologically evolved with human beings right so human beings that I'm sorry evolved with human beings is the premise to the conclusion that dogs are great pets for something okay since as indicated by because this is probably the most common in that may be inferred as given that seen that for the reason that that's pretty common I think since is a common one too so you can always number three right after you've looked for the where we have up here after you've asked what to take away is in search for the indicator term I guess then you take a look at the premise indicators right so number three search for the premise for the premises by taking a look at the indicator terms okay that's the sort of scroll down here okay so let's give some examples here these are some basic core examples you need to take a look at let's take this argument expected mothers should never use recreational drugs since the use of these drugs can jeopardize the development of the fetus okay so first off ask yourself one what's the takeaway well say it read it again expectant mothers should never use recreational drugs since uses these drugs can jeopardize the development is the takeaway is that pregnant women should use drugs okay which means that and notice here there was no indicator term we can just sort of sit back and figure out what it is best thing to do when you see this is underline the conclusion if you're if you're using a textbook or something like that underline the conclusion now let's take a look where's the premise well notice there's a there is a premise indicator term since the use of these drugs can jeopardize the developing fetus so this is we'll say this is premise one that's aureus that and this is conclusion one there's only one conclusion one premise here okay so that's an example of how you can do these problems do let's do another one here it's vitally important that wilderness areas be preserved for wilderness provides essential habitat for wildlife including endangered species and it is a natural retreat from the stresses of daily life okay this one is bright eyes this thing says this one is a little bit more difficult right so let's say first off let's ask ourselves what's the take away okay let's read it again it's finally important that wilderness areas be preserved for wilderness areas provides okay this word for this is a premise indicator term right this is what thought will comes after this is going to be a premise or a reasoning for willows provides essential habitat for web including the endangered species and look here we have another term and it is a natural retreat from the stresses of daily life so we see here is that this this first statement it is vitally important area that it is vitally important that wilderness areas be preserved this is the conclusion actually let's put c1 for conclusion and then here we have for wilderness areas provide essential area and is natural tree from stresses daily life this here is going to be premise you know to make it simple all circle the conclusion here right this is premise one and then this thing here this is premise two now what is this thing right here this is this is an indicator term but what's this and this in is going to be known as a conjunctive and don't worry too much about that right now but a conjunctive it means that it's a term that to conjoin two different premises together right so but you can see here the best thing to do because in the homework you do after this is you really just have to stop and just think slowly about what's being said here okay here's another example the space program deserves increased expenditures in the years ahead not only does the National Defense depend on it but the program will more than pay for itself in terms of technological spin-offs furthermore at current funding levels the program cannot fulfill its anticipated potential ok what's the conclusion the conclusion like the other ones we looked at sorry I raised it is this first statement the space probe deserves increased expenditures in the years ahead ok so this is the conclusion now not only does National Defense spin up but the program will more than pay for itself in terms of spin-offs you can see this is sort of a complicated one but this thing here is a premise right because this is trying to support the conclusion that we need more money for it right and then this furthermore this is another one of these conjunctive terms right at the current funding levels the program cannot fulfill its anticipated potential this is also a premise right this one allows them a little bit more tricky but again I think the simplest way is really to sit back and ask yourself what's the takeaway now you'll notice here I want to make a distinction here between statements let's just put this this is a distinction but you should know a difference the distinction is just talking about two differentiation something where two is two concepts that are different statements versus propositions okay and this is actually a very critical distinction within logic now what's a statement a statement is really the actual utterance or right or sentence this is the actual artistries that's normal and writing isn't it it's the actual utterance or it's the sentence itself whereas the proposition isn't the utterance but we say that the proposition is what is meant by the sentence for the utterance we're talk about the meaning okay so prostate mints right essentially this is the grammar this is that the sentence whereas the proposition here is the meaning it's the meaning of the claim so for instance think about like this let me say like this we can take this statement here the space program deserves increased expenditures in the years ahead and but the meaning is not the same is that right or doesn't have to be like this thing I can actually say that same thing differently I could say for instance NASA needs a greater budget so that NASA needs to spend more money I guess I says NASA deserves to spend more money in the future right that NASA needs to spend more money in the future means the space burbs the increasing expenditures in the years ahead right so I can have two different statements that are actually the same proposition and the reason that that's really actually important is because one of the things you're going to see him here is that as we go through as you go through this course is that oftentimes when you read when you read a full argument let's say in a newspaper or something like this let's say you read a newspaper editorial right where some sort of argument is being made oftentimes people will say the same thing in multiple ways which means they'll give multiple propositions right don't give multiple senses but all of them combined really there's just one proposition or just a handful just will put a handful of propositions right so one of the tasks you have to do when you evaluate arguments is figure out what the meaning of it is figure out what the propositions are and actually analyze the form that the propositions are given rather than the syntax the grammatical sentence structure right so this is a pretty important distinction to make as well because some so we've talked here about the idea that statement that's arguments and statements can have truth values there's such a things as non standards there's conclusion and premise indicator terms and also the difference here between propositions and one thing I forgot to mention that is in this chapter that's worth remarking here is the concept of inference right and this is sort of one of the things that's really exciting about this course and one of the things I think you'll find is if you do well in this course you actually have to sort of get interested and excited about this stuff and see it's something is sort of the game and rather than a pouring dry subject an inference what is the inference I said it right correct reasoning forms in such a sense that arguments can add truth functionality right and that means that the truth can flow from the premises necessarily to the conclusion this this notion of flow the Natalia is what I mean is really inference so that means that you can infer from the parenthesis the conclusion okay so inference is the technical term here to talk about how truth can flow from the parenthesis to the conclusion so that's what I want you to think of what we talked about inferences maybe not the most technical term for inference a technical definition but I think it's a very helpful one let's see here I want to show you let's exit this what's there I'm sorry let me show you this in fact let me give you the let me give you the exact definition here the customer booked any inference in the narrow sense this term is the reasoning process expressed by the argument we're now obviously a proposition in the narrow sense is the meaning or information content of the statement okay so that's the sort of general sense here about what the inference in a proposition are okay now there is a there is a note here about the history of logic that I'd like you to read in your book I'm going to cover this more in another lecture so most of the lectures here that I'm posting you're purely just about the mechanics of learning logic and the basic concepts we will be talking about the development of logic though and I'd like you to read these in the textbook we'll be talking about them later this mainly talks about the idea sort of gives you a brief overview of the history of logic beginning with Aristotle and I think working all the way up into contemporary mathematicians like Kurt kernel or for instance Bertrand Russell contemporary in the larger sense of the sense right they lived in the 20th century so but this sort gives you an overview but you'll see here they now that you've listened this video if you have the textbook and you're following along with the text that I'd like you to go here to exercise 1.1 or if you're using aplia you can use you can work on the problems that are aside for you you can see that what are you supposed to do in these exercises the first thing you're going to do is look for conclusions and premises right and you're going to sort of get arguments and then what you need to do is you need using the letters P and C identify the premise and conclusion of each argument oftentimes it's helpful to circle as a result for instance to circle these indicator terms right as a result was that a conclusion or a premise indicator term do you remember I hope you do okay and you can see that that's essentially what most of your homework is to for this section 1.1 is actually taking a look at these sort of core really simple arguments and then from there doing a short analysis in the second section here what's interesting is these are really real arguments that people have made okay and the following arguments in the sexy section which you're going to need to do is in order to fully understand you have to rephrase the conclusion right you have to move away from looking at the sentence or the statement in order to determine what the proposition is and then figure out it from there okay so that's essentially what your homework is for 1.1 now

Channel: Mark Thorsby

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Length: 35min 32sec (2132 seconds)

Published: Thu Aug 02 2012