Welcome to the next Behney podcast, which this time is on arguments.
Welcome to the people who are watching or listening to the podcast and welcome to everyone here.
And philosophers study logic and logic tells us how to distinguish good arguments from bad.
And there are many arguments, many problems that can be approached only by using logic.
So consider the following sentence. Therapeutic cloning is morally acceptable.
OK, just a reminder on what therapeutic cloning is. You can use the technology of cloning either for reproductive purposes where you produce it.
So you take the nucleus from a human cell.
You deem nucleate a cell from another animal,
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.
That would be reproductive cloning, therapeutic cloning. You would nucleate a cell, you would put the nucleus from the donor into that cell,
and then you would use the resulting embryo for research or maybe to harvest stem cells from it again for use in research.
So therapeutic cloning doesn't result in a live baby in this country.
It is legal, but only under certain very stringent conditions. And the resulting embryo must be destroyed by the 14th day, whereas of course,
for reproductive cloning, you hope that the embryo isn't destroyed at all.
So we're looking at the sentence. Therapeutic cloning is morally acceptable.
Some of us are going to believe that that's true.
OK, some people think that that therapeutic cloning is going to lead to discovery of cures for all sorts of diseases.
And for that reason, it's it's welcome and others or believe it's false.
So some people think that therapeutic cloning involves the destruction of very early embryos and that for that reason, it's wrong.
So there's a disagreement. Rational people disagree on this sentence.
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.
The only way we're going to determine whether it's true or false is by argument.
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.
You can only see the way something is. So determining morality is not something we can do in the laboratory.
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.
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.
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.
And when we construct an argument, we put forward a claim and one or more reasons for believing that claim.
And the claim we put forward is called the conclusion and the reasons for believing the claim of called the premises.
So here's an argument that at the moment isn't set out like an argument,
we have a duty not to exploit non-human animals, but when we engineer their genes, this is what we're doing.
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.
We shouldn't genetically engineer non-human animals and here are the reasons that are being given for that claim.
We have a duty not to exploit non-human animals and we exploit non-human animals when we use their genes.
So first premise, second premise and the conclusion that's the claim being made.
Those are the reasons being given for the claim. And when we set out an argument like this, we set it out.
Logic books style makes the structure of the argument very easy to understand that there are different types of argument,
but all of them fall into one of these two categories. They're either deductive arguments or they're inductive arguments.
We're either engaging in deduction or in induction. So let's have a look at the differences here on this side.
We've got a deductive argument. If the patient is in a permanent vegetative state, then he will not be conscious.
The patient is in a permanent vegetative state. Therefore, the patient won't be conscious.
OK, this is an inductive argument. People with Huntington's disease have always been observed to have the gene on chromosome four.
Therefore, the next person who develops Huntington's disease will be observed to have the gene on chromosome four.
Let's look at what the differences are between these two are.
Deductive argument is such that if it's valid and its premises are true, then its conclusion must be true.
And a deductive argument is either valid or invalid. It's an either or matter.
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.
That's the sort. OK, is this true here? So if that's true and that's true, must that be true?
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.
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?
And if it couldn't be, that's a deductively valid argument.
OK, with induction, it isn't like that.
OK, people with Huntington's disease have always in the past been observed to have the gene on chromosome four.
Does that mean we will of certainty see that the gene on chromosome four of the next person with Huntington's disease?
It seems hugely likely, but it's not absolutely certain.
Is it just possibly there are different variants of Huntington's disease and one type won't have that as a characteristic.
So where is the deductive argument is such that if the premise is true, the conclusion must be true with an inductive argument.
The premise could be true without the conclusion being true, even if it's hugely likely that the premise is true.
And again, with deduction, it's either or either the argument is valid or it isn't valid either.
If these premises are true, this conclusion will be true or it isn't.
The case will be looking at that in a bit more depth later on.
Let's have another look at a bit more.
So an inductively strong argument is such that if its premises are true, its conclusion is extremely likely to be true.
OK, not certain to be true as it was with induction. Inductive arguments can be strong or weak.
They're a matter of degree, whereas validity isn't.
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.
Do you see that? And we can also see that that's a very strong inductive argument.
And that's because we've got the word always in.
People with Huntington's disease have always been observed to have the gene on chromosome four.
Well, if it had been a few people have been observed to have that gene on chromosome
four when they had Huntington's disease would be much less confident of that.
And I'll show you in a minute another inductive argument where we wouldn't be confident at all.
So inductive arguments, even at their strongest, do not deliver cast iron guarantees,
all such arguments tacitly rely on what the philosopher Hume called the principle of the uniformity of nature.
This belief underlies all our empirical, all our scientific reasoning, and it can't be justified without circularity.
So imagine that we've seen the sun rise every single day in the history of the universe.
That makes us fairly confident that it's going to rise again tomorrow.
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.
So here a farmer comes this morning, used to be fed and instead you get your neck run because this is the morning,
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,
that doesn't justify us claiming that the future will be like the past in the future.
If you're with me, we can't, without circularity, justify the claim that nature is uniform,
because any claim that nature is uniform itself relies on the claim that nature is
uniform and because induction relies on the principle of the uniformity of nature.
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.
Without induction, science would be impossible. And the whole of science assumes that the future will be like the past.
If I can produce this result in my laboratory,
then I expect you work in your laboratory and reproducing my experiment to come up with the same results.
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.
And the examples I've offered so far have both been good arguments.
One was a valid deductive argument. The other was an inductively strong inductive argument.
But have a look at these arguments. If the patient is in a permanent vegetative state, then he will not be conscious.
The patient is not conscious, therefore the patient is in a permanent vegetative state.
What's wrong with that argument? We say, let's take a double that and the.
It could be lots of reasons to be unconscious. Absolutely, we can provide many counterexamples to this.
An account, for example, is a situation where the premises are both true and the conclusion false.
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,
but that many situations in which she's not MBBS, he's unconscious for some other reason,
maybe just fell off the stage and knocked himself unconscious or whatever.
So we can give lots of counterexamples to this. And therefore, that's a bad deductive argument is invalid.
It's not the case that there's no sorry there is a possible situation which the premise is true and the conclusion false,
and therefore the argument is invalid. And here's a bad inductive argument.
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.
Now we all think like this. Actually, we do. The thing about human beings is we can't not think like that.
If we do something and it's successful, the probability of doing it again is hugely raised.
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.
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?
Because actually this gives us hardly raises the likelihood of our passing the exam at all.
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.
I've just said that so we can skip on no, sorry, I said again.
OK, the argument on the on the right is an inductively weak argument.
Sorry, who started the argument on the left? That one is an invalid argument.
The premise of the argument, even if they are true, give us no reason to believe the conclusion, ok?
And then if we look at the one on the right, it's an inductively weak argument,
even if the premise is true, the likelihood of the conclusion is hardly raised at all.
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.
That's the argument on the right. A bad argument like the two we've just looked at tells us nothing.
But if we don't recognise it as bad, it can easily leave us astray.
Can you see that? Certainly. The argument on the left there,
many people would miss the fact that actually what you're doing there is affirming the consequent rather than arguing validly.
And if we don't recognise bad arguments as bad, it will lead astray.
So what we want to do is learn how to evaluate arguments properly and in evaluation argument.
There are two questions that we've got to ask. The first is, are the premises all true?
And the reason for this rather complicated syntax here is some arguments have only one premise.
There's no reason to think that an argument needed to have two premises or more than two.
And so is its premise. True is one question was asked. And the second question is, does the conclusion follow from the premises?
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.
Are the premises true? Does the conclusion follow? Those are the two key questions.
And looking at these, this is a very complicated slide and maybe I should have broken it up a bit.
But looking at the two questions, there are four possible answers to these questions taken together.
And it might be that the answer to both questions is yes.
Yes, the premises are true. And yes, the conclusion does follow.
And so the premises are all true. The conclusion follows in this situation,
the argument is said to be sound and the sound argument is exactly one where the premises are true and the conclusion follows.
A sound argument gives us excellent reason to believe the conclusion. It's very definitely a good argument.
OK, so if the answer to both questions is yes, yes, you've got a good argument.
If the answer to the first question is yes, but the answer to the second is no,
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.
And in this situation, the truth of the premises gives you no reason at all to believe in the truth of the conclusion.
The premises and the conclusion are not related in the right way to convince us of anything.
And so imagine, for example, that the premises of arguments three and four are true.
So the last two arguments we had, even if the premises are true,
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.
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.
OK, so the premises provide good reason to believe the conclusion.
The conclusion follows from the premises, but the premises aren't true.
So this argument is such that although its conclusion follows from its premises, at least one of the premises is false.
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.
But the fact that the conclusion follows from the premise means that the argument can be considered a good argument.
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.
Actually, as logicians, that's what we're concerned about.
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.
So we call that a good argument, which is distinct from a sound argument, which is a good argument with true premises.
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.
Well, what do we think about this argument? We think it should go in the bin.
It's a useless argument. It shouldn't convince you of anything. So two questions you should ask always.
Whatever your argument you're looking at, those are is premises true?
Does the conclusion follow from the premises?
There are four different possibilities if you ask those two questions, and those are the ramifications of the answers in each case.
And I'd just like to point out that the relation of following from covers to.
Different sorts of relation between a set of premises and a conclusion, so the conclusion of a deductive argument follows from its premises.
If the argument is valid and the conclusion of an inductive argument follows from its premises, if the argument is inductively strong.
So there are two different meanings for follows from depending on whether you're looking at a deductive argument or an inductive one.
And we're going to look at the difference between those two in the next podcast.
So in this podcast, we've considered what the two sorts of follows from have in common the fact that an
argument could get counted as a good argument only when it's valid or inductively strong.
And if you'd like to know more, here's the list of places you might go.
Thank you.