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Welcome to the next Behney podcast, which this time is on arguments.

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Welcome to the people who are watching or listening to the podcast and welcome to everyone here.

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And philosophers study logic and logic tells us how to distinguish good arguments from bad.

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And there are many arguments, many problems that can be approached only by using logic.

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So consider the following sentence. Therapeutic cloning is morally acceptable.

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OK, just a reminder on what therapeutic cloning is. You can use the technology of cloning either for reproductive purposes where you produce it.

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So you take the nucleus from a human cell.

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You deem nucleate a cell from another animal,

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you put the nucleus into the cell and then you plant it into the uterus of a female of the species and let it grow to term.

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That would be reproductive cloning, therapeutic cloning. You would nucleate a cell, you would put the nucleus from the donor into that cell,

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and then you would use the resulting embryo for research or maybe to harvest stem cells from it again for use in research.

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So therapeutic cloning doesn't result in a live baby in this country.

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It is legal, but only under certain very stringent conditions. And the resulting embryo must be destroyed by the 14th day, whereas of course,

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for reproductive cloning, you hope that the embryo isn't destroyed at all.

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So we're looking at the sentence. Therapeutic cloning is morally acceptable.

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Some of us are going to believe that that's true.

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OK, some people think that that therapeutic cloning is going to lead to discovery of cures for all sorts of diseases.

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And for that reason, it's it's welcome and others or believe it's false.

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So some people think that therapeutic cloning involves the destruction of very early embryos and that for that reason, it's wrong.

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So there's a disagreement. Rational people disagree on this sentence.

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And there's no way that any empirical study, there's nothing we can do in the laboratory to determine whether that sentence is true or false.

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The only way we're going to determine whether it's true or false is by argument.

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And the reason there's nothing we can do in the laboratory is because science in the laboratory, you can't see how something ought to be.

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You can only see the way something is. So determining morality is not something we can do in the laboratory.

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We can do it only by argument. So, as I say, there are some sentences, the truth or falsehood of which can be determined only logically.

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And those of us who think that moral therapeutic cloning is morally acceptable and those of us who think it isn't can't both be right.

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I've just said that, haven't I? OK, so we can only decide that's the truth of that sentence by engaging in arguments.

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And when we construct an argument, we put forward a claim and one or more reasons for believing that claim.

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And the claim we put forward is called the conclusion and the reasons for believing the claim of called the premises.

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So here's an argument that at the moment isn't set out like an argument,

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we have a duty not to exploit non-human animals, but when we engineer their genes, this is what we're doing.

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Therefore, we shouldn't genetically engineer animals. And when we put out that argument in the way I suggested, here's the claim that's being made.

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We shouldn't genetically engineer non-human animals and here are the reasons that are being given for that claim.

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We have a duty not to exploit non-human animals and we exploit non-human animals when we use their genes.

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So first premise, second premise and the conclusion that's the claim being made.

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Those are the reasons being given for the claim. And when we set out an argument like this, we set it out.

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Logic books style makes the structure of the argument very easy to understand that there are different types of argument,

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but all of them fall into one of these two categories. They're either deductive arguments or they're inductive arguments.

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We're either engaging in deduction or in induction. So let's have a look at the differences here on this side.

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We've got a deductive argument. If the patient is in a permanent vegetative state, then he will not be conscious.

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The patient is in a permanent vegetative state. Therefore, the patient won't be conscious.

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OK, this is an inductive argument. People with Huntington's disease have always been observed to have the gene on chromosome four.

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Therefore, the next person who develops Huntington's disease will be observed to have the gene on chromosome four.

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Let's look at what the differences are between these two are.

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Deductive argument is such that if it's valid and its premises are true, then its conclusion must be true.

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And a deductive argument is either valid or invalid. It's an either or matter.

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So let's go back and have another look at this. OK, so if the patient is so if the premises are true, the conclusion must be true.

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That's the sort. OK, is this true here? So if that's true and that's true, must that be true?

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I think you'll find that it does have to be. You can imagine all sorts of situations where that wouldn't be true and where that wouldn't be true.

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But we're not talking about those situations. We're talking about the situations where that is true and that is true and asking could that be false?

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And if it couldn't be, that's a deductively valid argument.

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OK, with induction, it isn't like that.

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OK, people with Huntington's disease have always in the past been observed to have the gene on chromosome four.

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Does that mean we will of certainty see that the gene on chromosome four of the next person with Huntington's disease?

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It seems hugely likely, but it's not absolutely certain.

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Is it just possibly there are different variants of Huntington's disease and one type won't have that as a characteristic.

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So where is the deductive argument is such that if the premise is true, the conclusion must be true with an inductive argument.

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The premise could be true without the conclusion being true, even if it's hugely likely that the premise is true.

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And again, with deduction, it's either or either the argument is valid or it isn't valid either.

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If these premises are true, this conclusion will be true or it isn't.

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The case will be looking at that in a bit more depth later on.

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Let's have another look at a bit more.

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So an inductively strong argument is such that if its premises are true, its conclusion is extremely likely to be true.

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OK, not certain to be true as it was with induction. Inductive arguments can be strong or weak.

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They're a matter of degree, whereas validity isn't.

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And again, let's go back and have a look at this so we see that if that's true, that may be hugely likely to be true, but it's not certain.

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Do you see that? And we can also see that that's a very strong inductive argument.

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And that's because we've got the word always in.

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People with Huntington's disease have always been observed to have the gene on chromosome four.

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Well, if it had been a few people have been observed to have that gene on chromosome

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four when they had Huntington's disease would be much less confident of that.

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And I'll show you in a minute another inductive argument where we wouldn't be confident at all.

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So inductive arguments, even at their strongest, do not deliver cast iron guarantees,

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all such arguments tacitly rely on what the philosopher Hume called the principle of the uniformity of nature.

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This belief underlies all our empirical, all our scientific reasoning, and it can't be justified without circularity.

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So imagine that we've seen the sun rise every single day in the history of the universe.

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That makes us fairly confident that it's going to rise again tomorrow.

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But of course, we could be in the position of Russell's chicken, who had seen the farmer coming out every single morning to feed it.

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So here a farmer comes this morning, used to be fed and instead you get your neck run because this is the morning,

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this is Christmas Day or something like that. And so just because the the in the past, the future has always been like the past,

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that doesn't justify us claiming that the future will be like the past in the future.

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If you're with me, we can't, without circularity, justify the claim that nature is uniform,

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because any claim that nature is uniform itself relies on the claim that nature is

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uniform and because induction relies on the principle of the uniformity of nature.

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That's why you don't get certainty. And I should point out that induction, the fact that induction doesn't give a certainty, doesn't make it inferior.

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Without induction, science would be impossible. And the whole of science assumes that the future will be like the past.

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If I can produce this result in my laboratory,

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then I expect you work in your laboratory and reproducing my experiment to come up with the same results.

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If you don't, then there's probably something wrong with my result because I expect my results to be replicable and so do you.

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And the examples I've offered so far have both been good arguments.

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One was a valid deductive argument. The other was an inductively strong inductive argument.

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But have a look at these arguments. If the patient is in a permanent vegetative state, then he will not be conscious.

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The patient is not conscious, therefore the patient is in a permanent vegetative state.

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What's wrong with that argument? We say, let's take a double that and the.

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It could be lots of reasons to be unconscious. Absolutely, we can provide many counterexamples to this.

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An account, for example, is a situation where the premises are both true and the conclusion false.

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And it could be true that if the patient is in a PVS, then he will not be conscious and true that the patient isn't conscious,

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but that many situations in which she's not MBBS, he's unconscious for some other reason,

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maybe just fell off the stage and knocked himself unconscious or whatever.

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So we can give lots of counterexamples to this. And therefore, that's a bad deductive argument is invalid.

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It's not the case that there's no sorry there is a possible situation which the premise is true and the conclusion false,

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and therefore the argument is invalid. And here's a bad inductive argument.

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When I passed that exam, I wore my red shirt. Therefore, if I wear my red shirt next time I take an example, pass that exam to.

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Now we all think like this. Actually, we do. The thing about human beings is we can't not think like that.

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If we do something and it's successful, the probability of doing it again is hugely raised.

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So if this is the situation, if and if it's the red shirt that seems salient to us, that's what will we'll do again.

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And even if we laugh at ourselves as we do it, we might still do it. But actually, that's a very poor argument, isn't it?

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Because actually this gives us hardly raises the likelihood of our passing the exam at all.

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So that's an inductively weak arguments. You see, again, that validity is a matter of either or, whereas induction is a matter of degree.

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I've just said that so we can skip on no, sorry, I said again.

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OK, the argument on the on the right is an inductively weak argument.

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Sorry, who started the argument on the left? That one is an invalid argument.

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The premise of the argument, even if they are true, give us no reason to believe the conclusion, ok?

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And then if we look at the one on the right, it's an inductively weak argument,

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even if the premise is true, the likelihood of the conclusion is hardly raised at all.

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So even if we're certain of the truth of the premise, this gives us very little reason to believe the truth of the conclusion.

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That's the argument on the right. A bad argument like the two we've just looked at tells us nothing.

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But if we don't recognise it as bad, it can easily leave us astray.

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Can you see that? Certainly. The argument on the left there,

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many people would miss the fact that actually what you're doing there is affirming the consequent rather than arguing validly.

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And if we don't recognise bad arguments as bad, it will lead astray.

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So what we want to do is learn how to evaluate arguments properly and in evaluation argument.

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There are two questions that we've got to ask. The first is, are the premises all true?

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And the reason for this rather complicated syntax here is some arguments have only one premise.

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There's no reason to think that an argument needed to have two premises or more than two.

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And so is its premise. True is one question was asked. And the second question is, does the conclusion follow from the premises?

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So whenever you're asking yourself whether an argument is a good argument or a bad argument, these are the two questions that must be asked.

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Are the premises true? Does the conclusion follow? Those are the two key questions.

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And looking at these, this is a very complicated slide and maybe I should have broken it up a bit.

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But looking at the two questions, there are four possible answers to these questions taken together.

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And it might be that the answer to both questions is yes.

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Yes, the premises are true. And yes, the conclusion does follow.

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And so the premises are all true. The conclusion follows in this situation,

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the argument is said to be sound and the sound argument is exactly one where the premises are true and the conclusion follows.

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A sound argument gives us excellent reason to believe the conclusion. It's very definitely a good argument.

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OK, so if the answer to both questions is yes, yes, you've got a good argument.

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If the answer to the first question is yes, but the answer to the second is no,

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then you've got an argument which is such that although it's all its premises are true, the conclusion doesn't follow from them.

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And in this situation, the truth of the premises gives you no reason at all to believe in the truth of the conclusion.

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The premises and the conclusion are not related in the right way to convince us of anything.

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And so imagine, for example, that the premises of arguments three and four are true.

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So the last two arguments we had, even if the premises are true,

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they don't give us any reason to believe the conclusion because the conclusion doesn't follow and those arguments can't be considered good at all.

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The third possibility is that the answer to one is no, the premises aren't true, but the answer to two is yes, the conclusion follows.

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OK, so the premises provide good reason to believe the conclusion.

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The conclusion follows from the premises, but the premises aren't true.

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So this argument is such that although its conclusion follows from its premises, at least one of the premises is false.

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In this situation. The fact that a premise is false means we haven't got reason to believe the conclusion despite its following from the premises.

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But the fact that the conclusion follows from the premise means that the argument can be considered a good argument.

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By that we mean as an argument, it's good and as we often don't know whether a premise is true or false or not.

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Actually, as logicians, that's what we're concerned about.

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What we're looking for is good arguments. We're looking for whether a conclusion follows from a premise rather than whether the premises are true.

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So we call that a good argument, which is distinct from a sound argument, which is a good argument with true premises.

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And finally, we might hit the situation where the answer to both questions is no, it hasn't got true premises and its conclusion doesn't follow.

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Well, what do we think about this argument? We think it should go in the bin.

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It's a useless argument. It shouldn't convince you of anything. So two questions you should ask always.

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Whatever your argument you're looking at, those are is premises true?

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Does the conclusion follow from the premises?

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There are four different possibilities if you ask those two questions, and those are the ramifications of the answers in each case.

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And I'd just like to point out that the relation of following from covers to.

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Different sorts of relation between a set of premises and a conclusion, so the conclusion of a deductive argument follows from its premises.

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If the argument is valid and the conclusion of an inductive argument follows from its premises, if the argument is inductively strong.

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So there are two different meanings for follows from depending on whether you're looking at a deductive argument or an inductive one.

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And we're going to look at the difference between those two in the next podcast.

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So in this podcast, we've considered what the two sorts of follows from have in common the fact that an

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argument could get counted as a good argument only when it's valid or inductively strong.

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And if you'd like to know more, here's the list of places you might go.

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Thank you.