Welcome to the fourth lecture on whom we're going to be talking today about Hume's most famous argument,
indeed probably the most famous argument in the English language philosophy.
His argument concerning induction and following that his theory of belief.
OK, so first of all, a reminder of where we were last time.
We're looking at treaties book one, part three. It's the longest part of the work on knowledge and probability,
but it turns out that the key to probable reasoning is going to be the relation of causation.
So in fact, it's Hume's quest for the analysis of causation that occupies the vast bulk of the part.
Now in section two, a book one, part three.
Hume starts off analysing causation. He identifies contiguity and succession as playing a role.
But he says that the main component of the concept of causation is necessary connexion.
There is a necessary connexion, we think, between a cause and its effect, and that is the key part of the idea.
But it seems quite elusive. So Hume sets off through two neighbouring fields to try to find a clue to where this necessary connexion might come from.
And one of those is to do with the causal maxim.
And then he turns to the discussion of inductive inference, causal inference, and that's how we get to treaties one three six.
OK. It's important to appreciate there are actually three presentations of this argument.
The first one is in the treatise.
That's obviously the one we'll be focussing on mainly, but it features very prominently in the abstract of the treatise, which was published in 1740.
Now we think that the abstract of the treatise was actually written in the autumn of seventeen thirty nine.
And bear in mind that books won. Two of the treaties were published at the end of January 17.
Thirty nine, so Hume was writing the abstract very soon after he published the treatise the first two books of the treaties.
But in the abstract, the argument concerning induction this argument is far more prominent and it is in the treaties.
I mean, the abstract is tiny compared with the first two books of the treaties,
but this argument in the abstract is about 75 percent as long as the original.
So he's only contracted that very slightly, and it's therefore interesting to see that Hume's philosophy is clearly changing during 1739.
He's appreciating that this argument, which really isn't very prominent in the treaties, actually deserves far more prominent.
It's far more significant than simply being a staging post on the way to the analysis of the idea of cause,
which is what it seems to be in the treaties and then in the enquiry 1748.
That very much follows the pattern of the abstract and section four of the enquiry where this argument receives its its fullest expression.
Again, that's really the centrepiece of the enquiry. So the arguments now very well known, very famous, very influential.
But looking at the treaties in its original form, you wouldn't see it as being such a major part.
Another point worth bearing in mind is that the argument in the enquiry in its final form is improved in various ways.
It's improved structurally. For example, it's streamlined.
So when you if you read the two together, you might find it a little awkward to kind of put them side by side and see them as arguing in the same way.
One particular difference is that in the treaties, Hume focuses on causal inference from the impression to the idea.
So we see a followed by B again and again and again, and then we see we get an impression of A.
And we find ourselves expecting B. So we have a vivacious idea of B an expectation that B will follow.
That is an inference from the impression to the idea in a specific case.
But in the abstract, in the enquiry, human broadens it, he says,
I'm concerned with any inference be on the present testimony of the memory and senses.
So anything that I'm not actually perceiving or remembering any matter of fact.
How can I infer such a matter of fact, and he says it has to be true causal inference.
So in the enquiry, he starts out with that epistemological investigation.
How can we discover things which we're not perceiving or remembering?
He says it must be by means of a causal inference. Now let's investigate that.
Whereas in the treaties, he starts out with the inference from the impression to the idea,
a specific causal inference and probable inference in general only comes into the picture later on when he's discussing the uniformity principle.
So the argument in the treaties is actually in in this way more convoluted than the one in the enquiry where he identifies probable reasoning,
the causal reasoning right from the beginning.
OK, so the argument initially the first the first part of the argument is to show that causal inference cannot be a priority.
We've got that whenever we make an inference from one thing to another, according to Hume, that's assuming some causal relation between them.
How can we find out about causal relations will only by experience?
Now in the treaties, humour argues that this is the case because whenever we perceive a cause or
what we take to be a cause we can imagine anything following is its effect.
We can conceive of any different causal relation, take any object.
It could be followed by any other as its effect and the mere conceive ability that something different could happen from what we expect.
That's enough to show that the inference from the course to the effect cannot be a priori.
At least that's what Hume seems to be arguing in the treaties.
So he seems to be assuming that if you have an April try inference, it has to yield total certainty.
Now in the enquiry. He doesn't argue like that.
He argues far more powerfully, he says, in advance of experience.
It's not just that we can conceive other things happening, but actually in advance of experience.
Any expectation would be completely arbitrary.
So it's not just that other things are possible, it's that we've no reason whatsoever for expecting one effect rather than another.
And he gives a thought experiment of Adam. And he introduces Adam in the abstract with billiard balls.
And he we have Adam, seeing one billion bill moving towards another.
He's just been newly created by God. He's got perfect human faculties and God asks him what's going to happen when the one bill hits the other?
Well, in advance of experience, Adam wouldn't have a clue. And that's a very powerful thought experiment,
I think you put yourself in the position where you have no experience of bulls at all and you're asked to predict you couldn't do it.
So it's not just that you could conceive of different things happening actually a priori,
you'd have no reason whatsoever for preferring one thing rather than another. So it's a much more powerful argument than the one in the treaties.
The argument in the treatise has led some people to think that humans are deductive,
that he takes for granted that the only legitimate method of inference is deductive.
Because it's enough to be able to conceive something different to undermine any argument, you don't get that impression from the enquiry.
He's just saying, you know, in advance experience, it's completely arbitrary. You'd have no ground, whatever for preferring one thing to another.
So here is the text where he he says that where any object presented to us and where we required to pronounce
concerning the effect which will result from it without consulting past observation after what manner I beseech you,
must the mine proceed in this operation?
It must invent or imagine some event which it ascribes to the object as its effect and its plain that this invention must be entirely arbitrary.
OK, so if we can't infer from calls to effect a priori, how does experience make a difference?
Well, experience makes a difference, Hume claims, because when we see a followed by B repeatedly,
when we see an air, we expect to be his a couple of passages from one three six.
Now notice the second passage here, having found that this is the experience that characteristically makes us infer an effect from a cause, he says.
Oh, we've discovered a new relation between cause and effect.
Right. We had priority and contiguity.
We noticed way back in one three two that they weren't enough, that there was this necessary connexion to be taken into account.
We've now found a new relation, but the relation is constant conjunction.
And it's very clear that this passage here from one three six three is linking back to one three to 11 both the phrasing and the capitalisation.
So it's indicative that humans are seeing constant conjunction as the key to necessary connexion.
And this is where he identifies that one important thing the the text from one three two is sometimes misinterpreted.
People say humans saying there is a necessary connexion to be taken into account.
That's obviously more than constant conjunction. No, he's not saying that.
If you look back at one three two, he's talking about a single case priority and contiguity,
and he's saying there is something else beyond in a causal relation.
Now he's saying, Oh, I found this something else. The something else is constant conjunction.
OK. So it's very important when you read necessarily connexion in one three to don't
take for granted that human there is meaning some what we call now a thick,
necessary connexion. That's something that goes beyond Hume's analysis of causation.
There's no evidence for that at all. And one three six is making clear that he is seeing constant conjunction as providing the key there.
So we'll talk later, obviously, about Hume's analysis of causation, but that that passage from one three two is quite often misunderstood.
OK, so what is the link between necessary connexion and constant conjunction?
Well, perhaps it will appear in the end that the necessary connexion depends on the
inference instead of the inference is depending on the necessary connexion.
That's a clue to what's going to come. Humans going to discover that it's the inference is that we make in response to
observed constant conjunction that give rise to the idea of necessary connexion.
So you might naturally think that when we make a causal inference, we start with the idea of necessary connexion and use that to make the inference.
He's saying it's the other way round. Actually, we find ourselves making an inference.
That's how we get the idea of necessary connexion. Now, as we saw last time, he frames his discussion in terms of faculties,
the next question is whether experience produces the idea by means of the understanding or imagination is the reason.
Or is it associational processes? And remember that understanding and reason are synonyms for Hume.
At least they are. The vast majority of cases they are. And here you can see he is alternating between the terms of elegant variation.
He's going to argue that reason cannot ground the inference,
and he's going to conclude that therefore it's imaginative process is a process he will call custom.
That does say. Well, let's ask ourselves again, we're making causal inference, imagine ourselves in the position of Adam.
A priority. We cannot infer from one thing to another. How does experience make a difference?
Well, it makes a difference because we find ourselves extrapolating from what we've seen.
We've seen a followed by be. We now expect that they will continue to be followed by be.
So we need to appeal to something that's commonly called the uniformity principle.
Hume doesn't call it the uniformity principle, but most Hume scholars do useful term now in the treaties.
The uniformity principle is introduced very explicitly if reason determined us.
In other words, if Reason was responsible for a causal inference,
it would proceed upon that principle that instances of which we have had no experience must resemble those of which we have had experience,
and that the course of nature continues always uniformly the same.
Now, I think the phrasing of that is slightly unfortunate and misleading.
Because it gives the impression that Hume here is saying something conditional, if reason determined does, then it would proceed upon that principle.
Now this is the only case in which the uniformity principle is put in a conditional way.
Later in the treatise, he says probability in a probable argument is founded on the presumption of a resemblance in the enquiry.
All our experimental conclusions proceed upon the supposition that the future will be conformable to the past.
That's not conditional it saying we do assume the uniformity principle.
And we find that in other passages, too, so so that that initial presentation in the treaties is actually unique,
it's the only case where he says if reason determined us, then it would be using the principle.
Notice also that the original presentation in the treatise looks rather implausible, he says the course of nature continues always uniformly the same.
It doesn't continue always uniformly. The same does it?
What we assume is that the same basic laws are applying the forms of the uniformity principle in the enquiry of Vega and hence actually better.
We take the past as a rule for the future, we suppose that similar causes will have similar effects.
Now, importantly, Hugh does not think that when we make an inductive inference, we explicitly ponder the uniformity.
OK. Indeed. Later in the treaties, he will say quite explicit.
That's not the case. And most inductive inferences are unreflective, we see, and we just expect to be.
We don't think about the uniformity principle. So there is a question about what role the uniformity principle is playing for him.
And I think I'm not alone in this that the most plausible way of taking this is to say that when we make an inductive inference,
we manifest our commitment to the uniformity principle.
The very fact that we're making the inference shows that we are taking the past as a rule for the future.
So it's not that the uniformity principle is acting as some premise in our reasoning,
but we are taking it for granted when we make an inductive inference. OK, so we still get the same question.
Does the uniformity principle, does our supposition of the uniformity principle?
Does that have a rational basis? Now in the treaties, immediately after he's introduced the uniformity principle,
he focuses on the question of whether it can be founded on some kind of ratty assassination,
some kind of stepwise argument in order therefore to clear up this matter.
Let us consider all the arguments upon which such a proposition may be supposed to be founded.
And as these must be derived either from knowledge or probability,
let us cast our eye on each of these degrees of evidence and see whether they afford any just conclusion of this nature.
And he's saying knowledge and probability. The very next sentence makes clear he means demonstration and probable argument.
So we've got two different kinds of arguments that could be used to support the uniformity principle, demonstrative and probable.
So let's just have a few slides on this distinction, the distinction between the demonstrative and probable reasoning.
It's more or less the same as the modern distinction between deductive and inductive argument.
This doesn't mean formally deductive, by the way. Human, like most philosophers of his period, was completely disdainful of formal logic.
So when we say an argument is deductive, fully valid when talking about Hume, we do not mean formally valid.
What we mean is it's an argument in which if the premises are true, the conclusion cannot possibly be false.
OK, so the conclusion follows from the premises with absolute and complete certainty.
But that needn't be in virtue of its logical form. OK.
Improbable reasoning, by contrast, the links that constitute the argument are merely probable, not demonstrative.
They don't follow with complete certainty. Now, Hume, again here he I've already noted his fondness for elegant variation,
like talking about reason and the understanding or imagination and the fancy,
and I'm afraid with regard to probable reasoning, he does something of the same.
So in the treaty as he normally does refer to it as probable reasoning in the same way that Locke does in the enquiry, he doesn't.
And the reason is that Hume thinks the talking of the word probable when we're talking about completely certain inferences like,
you know, I hold up a stone and I let go of it. And I'm absolutely certain that it's going to fall, OK?
It's not demonstrative, but but inductively certain that it's going to fall.
And Hume thinks it's in this to talk about that as merely probable.
He says it's a proof I've got uniform experience.
So he doesn't actually want to use the word probable to talk about probable arguments in the way that locked it.
He wants a different name for the for the broader category of inductive arguments, some of which he thinks yields complete psychological certainty.
And some of which don't.
So he calls them reasonings concerning matter of fact or reasonings concerning matter of fact, an existence or moral reasoning.
So if you see the term moral reasoning, he's talking about this same category.
So when I'm discussing Hugh, Mike quite often used the word factual reasoning, and that's just shorthand for reasoning concerning matter of fact.
OK, so we've got two different forms of reasoning, demonstrative and probable,
and I've said they're more or less the same as deductive and inductive in in our modern usage.
Now that's actually a little bit controversial because some scholars have thought that when Hume talks about demonstrative argument,
he must be confining it to deductive arguments that a priori.
And there are two main reasons why people have thought this.
I think, by the way, it's certainly wrong and I'm going to explain why.
But the the two reasons why people have thought this is that Hume says that no matter of fact, can be demonstrated.
And some people have taken this to mean that according to him, no matter of fact, can be the conclusion of a demonstrative argument.
Now, I think those are just different things.
OK, so suppose I've got an argument which is disruptively valid and it's got three premises P1, P2, P3 and Conclusion C. And it's a valid argument.
OK. Can I be said to have demonstrated C? No, because P1, P2, P3 might be controversial.
You might not believe those in which case you're not going to agree that I've demonstrated c all I've done is demonstrated C from P1, P2, P3.
So you never says that a matter of fact can't be the conclusion of a demonstrative argument, he says.
No matter of fact can be demonstrated. So. So much for that first reason,
the second reason is this that Hume does say explicitly in both the treaties and the enquiry that
only in mathematics does demonstrative argument apply or does it apply to any significant extent.
So in the enquiry, it seems to me that the only objects of the abstract sciences or of demonstration are quantity and no.
The team gives his reason for this. The reason why demonstration, he thinks, is more or less restricted to mathematics.
Is because only in mathematics do you get ideas that are sufficiently precise with intricate relations that you can follow a long chain of reasoning.
So outside mathematics, Hume thinks demonstrative arguments tend to be trivial.
Like, you can conclude that where there is no property,
there is no injustice by defining justice as a violation of property, he gives this as an example in the enquiry.
But that's just trivial. So it's only in mathematics.
He thinks that demonstration that he's particularly complex demonstration really gets a foothold.
The the obvious crucial case that we need to look at in order to sort this out is applied mathematics,
because in applied mathematics, you get complex mathematical reasoning, but it starts from a posterior right premises.
So a philosopher who accepts the existence of applied mathematical demonstrations is not assuming that demonstration is a priori.
Well, Hume's most explicit discussion of applied mathematics, he calls it mixed mathematics is Enquiry Section four.
It's a law of motion discovered by experience that the moment or force of any body in motion.
Think of that as momentum is in the compound ratio or proportion of its solid contents tense and its velocity
momentum is mass times velocity and consequently that a small force may remove the greatest obstacle.
If by any contrivance, we can increase the velocity of that force so as to make it an overmatched for its antagonist.
So here's an illustration. We've got a large body moving to the left at four metres per second.
We've got a very small body. If we move it to the right fast enough, it will displace the large body.
It'll make it move in a different direction, it seems to me. Hume is clearly expressing something like this.
OK, so mathematics can assist us in working out the implications of the law.
But the discovery of the law itself is owing merely to experience and all the
abstract reasonings in the world could never give us any knowledge of it.
So humans being absolutely explicit here, the law of conservation of momentum is discovered by experience,
and then mathematics can help us to apply it. So it's very clear Hume does not restrict demonstrative reasoning to a priori reasoning.
OK, so as I mentioned in the treaties,
having brought in the uniformity principle and said that all our inductive inferences depend on this depend on this extrapolation from past to future.
He's now asking. Can the uniformity principle be supported by either demonstrative argument or probable argument?
As I say, by deduction or inductive argument, as we would now say now in the enquiry, the argument is more complete.
He doesn't just restrict his discussion of the uniformity principle to demonstration and probably argument.
He also takes the trouble to rule out that sensation could provide a basis for the uniformity principle.
And he also also rules out intuition what we would call self-evident.
There is no known connexion between the sensible qualities. That's the sensory qualities and the secret powers.
And consequently,
the mind is not led to form such a conclusion concerning their constant and regular conjunction by anything which it knows of their nature.
So think back to the Adam thought experiment. Adam sees the sensory qualities of the ball and the shape the colour.
He cannot infer from that what's going to happen. But nor can he infer from that that what will happen will be consistent over time.
So therefore, sensation alone does not give us a basis for expecting consistent behaviour.
It doesn't give us a basis for extrapolating from past to future.
But also, the connexion between past and future is not intuitive,
it's not self-evident that what happens in the future will resemble what happened in the past.
So the enquiry argument, as I say, is more complete.
And rather nicely, the letter from a gentleman to his friend in Edinburgh, which you published in 1745,
so we've got the enquiry appearing 17 48 in 1745, Hume applies for a chair of Edinburgh.
He wants to be a professor of philosophy at Edinburgh New medical philosophy, so he would be talking about the soul and so, so forth.
Not surprisingly, the clerics of Edinburgh weren't best pleased with this.
They didn't want somebody who had written the treatise of human nature,
which seemed rather atheistic to be becoming a professor of new mystical philosophy at Edinburgh.
And so they stirred up a hubbub against him, and Hume wrote this letter from a gentleman to his friend in Edinburgh in order to
defend himself in order to say the treaties isn't as bad as it's been painted.
Now, the letter from a gentleman was written while Hume was actually acting as a tutor for a madman,
the man the Marquess of Annandale, out in the country.
He did not have the treaties with him, so he wrote this letter to the people in Edinburgh.
The relevant people? Actually, it was Henry Hume who I mentioned in the first lecture who who got this published on his behalf.
He wrote this letter defending himself about the philosophy of the treaties, but without actually being able to quote the treaties itself.
So the letter is actually a very interesting document for getting insights into Hume's thought,
and this sentence is, I think, particularly illuminating. It is.
So you're saying in order to explain my position on the causal maxim because that had been picked up by his critics,
I mentioned the causal maxim plays a big role in arguments for the existence of God in the cosmological argument.
So that was a matter of considerable interest says. In order to explain my position on the causal maxim,
I need to tell you that it's common for philosophers to distinguish the kinds of evidence into intuitive, demonstrative, sensible and moral.
And all I was doing in treaties one, three three was denying that the causal maxim can be based on either intuitive or demonstrative evidence.
I wasn't denying it. On the contrary, I said that the causal maxim is based on moral evidence on probable argument.
No, you didn't. Hume, you forgot to say that in the treaties, but evidently he intended to say.
OK, now what's particularly interesting here is that we've got four forms of evidence they're intuitive, demonstrative, sensible, moral and human.
And the enquiry is explicitly ruling out each of these as a basis for the uniformity principle.
And again, we've got that letter being written no doubt at the time that he was working on the enquiry.
OK, so. In the treaties and in the enquiry,
demonstrative argument for the uniformity principle is ruled out in the same way we can at least conceive a change in the course of nature,
which proves that such a change is not absolutely impossible and that yields a refutation of any pretended demonstration against it.
If you could demonstrably demonstratively prove the uniformity principle, you know, e.g. by arguing from past uniformity to future uniformity.
And then that would mean that it was inconceivable that the course of nature would change.
But it's not inconceivable. Therefore, you can't have such an argument and probable argument.
You can't have a probable argument for the uniformity principle because probable argument itself depends on the uniformity principle.
Now, this is where the intelligence in the treaties argument comes out, because as I said in the treaties,
the argument starts from the inference, from the impression to the idea.
He hasn't actually mentioned probable argument in general yet.
He only comes to mention it when he discusses the ways of supporting the uniformity principle.
And then when he comes to that, he has to go back to square one and say, Can the uniformity principle be sought supported by a probable argument?
Well, no, because probable argument depends on causation, and causation depends on experience,
and therefore it depends on the uniformity principle and therefore we've got a circularity. In the enquiry, right at the beginning of the argument,
Hume has said I am concerned about all inferences from things directly perceived or remembered to other matters of fact.
So all inferences concerning matter of fact, I found it on causation and therefore on uniformity.
So he's already proved that general point before he comes to ask the question about the uniformity principle.
So I've got here a couple of slides that summarise the structure of the argument to some extent,
you know, I'm shoehorning the argument into a particular structure,
but I think it's quite illuminating that the structure of the argument can be revealed by thinking in terms of the founded on relation.
So I'm not claiming that Hume expresses it in this way. I'm not claiming that in every case, Hume uses the term founded on.
But if you think through the logic of the arguments in this way, I think it can help.
So what we've got there at the top is that he argues that causal inference is founded on experience,
that reasoning from experience is founded on the uniformity principle.
And he concludes, therefore, that causal inference is founded on the uniformity principle.
OK. But the uniformity principle can't be founded on demonstration.
Nor can it be founded on probability. So that's the weather you can see that you can't if you look at the the yellow box in the middle there,
that's saying it's not the case that the uniformity principle is founded on probability,
but you can see that in order to reach that lemma, he's having to go through at the bottom.
The same argument that he started with, we've got a repetition within the argument.
And then because uniformity principle is not founded on demonstration and is not founded on probability, that's the two yellow boxes.
He concludes that the uniformity principle is not founded on reason and because causal inference
is founded on the uniformity principle in the uniformity principle is not founded on reason.
It follows that causal inference isn't founded on reason. By the way, that last stage of the argument is an interesting one.
Some interpretations of Hume's argument, I think, cannot make sense of that final stage, but I'm not going to focus on that here.
Is the argument in the enquiry? It's much more elegant and it's more complete.
You can see right at the top, he starts with probable inference. He's founded on causation.
Any reasoning from causation is founded on experience, therefore probable inference is founded on experience.
Any reasoning from experience is founded on the uniformity principle. Therefore, probable inference has to be found on the uniformity principle.
So he's got that right at the start, and you can see at the bottom there, we've got that.
The uniformity principle isn't founded on intuition, and it's not founded on sensation either.
And it's not founded on demonstration,
and it can't be founded on probability because probability probable argument is founded on it on the uniformity principle.
So when Hume concludes that the uniformity principle isn't founded on reason in the enquiry,
he's drawing that conclusion from the fact that none of the four forms of evidence can support it.
OK. The sceptical conclusion notice, I'm putting the word, I'm putting the word sceptical in quotes here.
It's debateable how sceptical Hume actually is about induction.
He is. He continues to be a supporter of induction.
He's certainly not saying that we should not use induction for drawing inferences about the world he thinks is the only way we can.
But on the other hand, there is something sceptical about the conclusion of this argument.
He is denying that induction has a rational basis of a kind that somebody might have thought it would have.
Even after experience has informed us of constant conjunction,
it is impossible for us to satisfy ourselves by our reason why we should extend that experience beyond
those particular instances which have fallen under our observation and later in the treaties one,
three, 12 20, as I mentioned there. He makes the same point even more emphatically.
We have no reason for drawing any inference beyond things we've experienced.
And there's a couple of quotes from the enquiry there. I think the last quote here probably gives the most precise version of Hume's conclusion.
And by the way, Don Garrett agrees with me on that.
We interpret the argument differently in various ways.
But in recent work that he's published, he has very much focussed on on this issue that there is a step in all inductive inferences,
which is not supported by any argument or press the understanding. So.
This is tricky because when we interpret Hume's conclusion, Hume's Hume's conclusion that inductive inference is not founded on reason in some sense.
How you interpret that is going to depend on how you interpret human reasons, so we come back to this question about how we should understand.
Faculty talk and as I mentioned in the last lecture, there's a lot of variation here.
So we've got the extrapolation from observed to unobserved is a step taken by the mind,
which is not supported by any argument or process of the understanding. What exactly is that ruling out?
Well, according to Beecham and Rosenberg and Beecham and Mathis, somebody else, he wrote, with all humans ruling out is a priori demonstration.
Pretty sure that's wrong. According to David Owen, all that's being ruled out is lock lock in stepwise inference,
according to Lerve non associative reasoning, according to Don Garret.
For the human reason just means ratty assassination argument.
It's not normative, it's purely descriptive.
And you can see now why Don Garrett is very keen on this law's quotation because many of our inductive inferences do involve complex rattus a nation,
I suppose. For example, we draw inductive conclusions about the motion of the planets.
That's going to involve a lot of Rattus in Asian.
But there is a step taken by the mind, namely the infants and past the future, the supposition that laws will continue the same.
That step is not founded on Ratti as a nation.
So by focussing on the individual step within the argument, Don Garrett is able to square Hume's conclusion with his interpretation of reason.
Now, a related question is whether houM views his discussion of induction as being epistemological or psychological.
And Don Garrett puts the emphasis on psychology, he says Hume is talking about the processes that go on in our mind when we make inductive inferences.
And according to Don, we don't make those inferences because we have been persuaded by some rational nation to do it.
My interpretation of humour and reason is that reason is the cognitive faculty,
so I take Hume's conclusion to actually have epistemological bite when we draw an inductive inference.
We're not doing it because we have cognisant that the future will resemble the past.
We're reading that into the world rather than reading it off the world.
Now, actually, I mean, there's quite a subtle difference between those two. I'm not going to discuss that debate.
There's plenty you can read in the literature on that, and I will be giving you a handout with readings next time.
But if we ask, is Hume's discussion epistemological or psychological?
It seems to me the answer is both.
Hume is drawing a conclusion about the psychology of our inductive inference, but he's doing it by revealing a certain impossibility.
He's not just saying, look at the way we do inductive inference, we do it immediately and instinctively.
He does say that later in the treaties. But that's not what he's saying in one, three six.
And it's not what he's saying an enquiry for what he's saying there is we could not possibly do it any other way.
We could not possibly do it using reason. And that is, it seems to me, an epistemological conclusion.
So humans drawing an epistemological conclusion, but using it then to draw a psychological conclusion,
we could not possibly do it that way and therefore we don't do it that way.
OK. So briefly, now I want to run through Hume's alternative theory.
How do we actually do inductive inference?
Well, of course, he says it's due to something like the Association of Ideas.
So we've seen that when our minds wander. They standardly move according to three associative relations,
if I'm thinking about something on my mind may be drawn to something that resembles it or something that's contiguous to it,
or something that is related causally to it. And now he's going to explain that inductive inference is due to a similar kind of associational process.
It's not quite the same. It's not mere association of ideas. But it's rather similar when I see a followed by B again and again and again,
it sets up an associational link between my ideas of A and B so that if I think of a, I may think of B.
Yes, that would be normal association of ideas. But when I actually see an impression of a.
The fulsome vivacity of that impression is conveyed to the associated idea, and as a result, I come to actually believe that be will happen.
That's not just association of ideas, it's a process that Hume calls custom.
And. Hume is not negative about custom.
You might think he would say, like Locke would have said, oh,
if induction isn't due to reason, if it's due to custom, then it's somehow not respectable.
He does not say that custom is the great guide of human life.
It is that principle alone which renders our experience useful to us.
It's only thanks to custom that we are able to draw inferences about the unobserved custom leads us to
just assume that the unobserved will resemble the observed and therefore enables us to make inferences.
He custom came up before in Hume's discussion of general ideas in one one seven, and here he does draw that link.
OK, now recall that before Hume came to induction, he was setting an agenda.
He wanted to explain the original impression of the senses or memory from which causal inference standardly starts.
He wanted to explain the transition, the actual inference, which is what he's just done.
And then he wants to explain the nature of the idea that such an inference delivers.
That is the belief that B will occur. And so he's now going to talk about the nature of belief.
So. The definition of an opinion or belief is that is an idea related to or associated with a present impression.
So I see a I've got an impression of a that enlivens the idea of B.
That is a belief that the will occur. It's an enlivened idea of B.
And. I think it's worth noting that the humour here is addressing an issue that would
later be identified by Fraga when Fraga was developing his logical system,
which of course was the ancestor of the logical systems that we studied today.
And. He pointed out that there's a difference between contemplating a proposition and actually asserting it.
So if you have a conditional like implies, Q, P and Q are both propositions, you're not actually asserting P and you're not asserting Q.
You might not even be asserting P implies Q, you might just be contemplating that conditional.
So there's a difference between contemplating a proposition and actually asserting it.
And what Hume is pointing out here is there's a difference between contemplating a proposition and actually believing it.
So what is the difference between those two?
Well, it can't be down to having some idea of existence, which somehow we attach to the proposition, you know,
maybe I'm I'm I'm thinking about some proposition and then I attach the idea of existence to it to bring it about that.
That's a belief that's not going to be the answer. And if we contemplate a proposition and then come to believe it.
It needs to be the same proposition, so we can't change the content of it.
So the difference, Hugh says, must lie in the manner in which we conceive it, the force and vivacity with which we contemplate it.
So the difference between contemplation and belief is going to come down to fulsome and vivacity.
So an opinion, therefore or belief, may be most accurately defined.
A lively idea related to or associated with a present impression.
So we get a definition of belief in terms of the theory of customary inference.
So. We've seen that causal reasoning has to start from an impression of the senses or memory.
I put that in quotes because strictly the ideas we have in memory are ideas, not impressions.
But as we saw before, Hume thinks they have additional vivacity because they're in the memory.
And that's enough to enable them to serve as impressions for the purpose of causal inference.
And we've seen that belief is distinct from mere contemplation of an idea in terms of false and veracity.
So it seems that when something becomes believed, what's happening is that we have what I've called a hydraulic theory of belief.
We've got the false vivacity of the impression is conveyed by the associative link to the idea, and that's what gives it this greater vivacity.
I've already alluded to this, but here we have Hume coming to this theory when any impression becomes present to us.
It not only transports the mind to such ideas as it related to it, but likewise communicates to them a share of its force and vivacity.
And Hume gives various illustrations to show that indeed,
Association of Ideas does have this feature that it communicates force and vivacity from one idea to another.
And later in the treatise, we see him applying a similar idea to probability if I've seen is sometimes
followed by bees and sometimes followed by CS with a particular probability,
a particular frequency in the past.
Then when I see an A, the force and vivacity of that impression is conveyed to the different outcomes in proportion to their past frequency.
So I will come to have a proportional belief in B and C.
Now, all of this isn't entirely satisfactory. It looks philosophically rather crude.
I mean, what is this force and vivacity? How does it really fit into the theory of ideas?
Is it the case that you really can distinguish? And I contemplated idea from a belief in terms of a single feature, fulsome vivacity,
which is the same thing that distinguishes ideas of memory from those of imagination,
which is the same thing as those is what distinguishes impressions from ideas.
This seems somewhat implausible. Moreover, more crudely, something I brought up in the second lecture when we were talking about the theory of ideas,
a fictional story can be much more forceful and vivacious than a dull historical account.
So in exactly the same way as watching paint dry can be much duller than imagining being attacked by spiders.
It's simply not true,
the things that we take to be actual perceptions or beliefs or reports about real things are always going to be more vivid than imagined things.
Now, in the appendix to the treatise, which was published the very end of October,
beginning of November 17 40, this was published along with Book three of the Treatise of Morals.
We get some symptoms of unease. Hume is saying an idea assented to feels different.
And when I talked about that feeling, I use terms like false and vivacity.
But you know? You know what I mean when I talk about belief?
It feels different, doesn't it? You know the feeling. You know what it's like to have a belief.
That's what I'm talking about, that feeling. And well, that's all very well.
But it's not so clear now that the hydraulic theory is going to work.
If I am asked to contemplate the difference between a belief and an idea between a memory and a mere imagining,
between an impression, an idea, yeah, I know what those things feel like in a sense.
Is it actually one in the same thing marking the difference there?
No, it isn't. So the hydraulic theory is probably going to have to go.
In the enquiry, Hume says quite explicitly, you cannot define belief.
So that's a contrast with the treaties. He repeats some of the words that he used in the appendix when he was showing his unease.
And when he comes to discuss probability in section six of the enquiry, instead of giving a hydraulic theory,
he says that such belief arises from an inexplicable contrivance of nature.
But frankly, the hydraulic theory is not really the main point of Hume's analysis of induction.
What's revolutionary about Hume's analysis of induction is his identification that when we make an inference,
an inductive inference, whenever we infer from observed to unobserved,
we are taking something for granted which we simply cannot give any basis for other
than the fact that we are naturally inclined to to reason that way to think that way.
So what we call reasoning about matter of fact is actually, in some ways, more like feeling than it is like rational inference,
we feel ourselves committed to the view that the same will happen in the future as the past.
We cannot give a reason for that fundamental assumption, which is absolutely basic to all of our thinking about the world.
That's all probable reasoning is nothing but a species of sensation, OK, that's a bit of hyperbole.
But when I'm convinced of any principle, it is only an idea which strikes more strongly upon me.
When I give the preference to one set of arguments above another,
I do nothing but decide from my feeling concerning the superiority of their influence.
As I say, that's somewhat hyperbolic. But the crucial point is that human nature is playing a fundamental role when we make inductive inference.
It is nothing like the kind of conception of rational thinking which had dominated previously.
And here we've got a quotation from Locke's essay where Locke is saying is saying about probable inference.
Inference consists in nothing but the perception of the connexion. There is between the ideas in each step of the deduction,
whereby the mind comes to see either of a certain agreement or disagreement of any two ideas, as in demonstration in which it arrives at knowledge.
Or this is the crucial bit the probable connexion on which it gives or withholds its assent as in opinion.
So in a probable argument, there are probable connexions between the different steps of the inference for as reason
perceives the necessary and indubitable connexion of all the ideas of or proofs by proofs,
he means intermediate ideas one to another in each step of any demonstration that produces knowledge.
So it likewise perceives the probable connexion of all the ideas or proofs one
to another in every step of a discourse to which it will think assent due.
So Locke thinks that when we do a probable argument, we are perceiving probable connexions.
Hume says that's nonsense when we do a probable argument.
There is at least one step where we infer from observer to unobserved, where we are not perceiving anything at all.
There's no cognition going in there.
It's an operation of the imagination we are reading into the world an expectation of uniformity for which there is no rational basis.
Thank you.