Hume's Irrationalism

What question did Hume ask about the external world?

Can we have any epistemically justified beliefs about the external world?

What is a Justified True Belief?

A belief that is true and corresponds to how things really are, independent of our beliefs.

What is A Posteriori justification?

Justification based on experiential states, such as senses or introspection.

What is A Priori justification?

Justification that is independent of prior experience.

Give an example of A Posteriori justification.

I would be justified in believing that fish exist, that fish can swim, that I am thinking about fish right now.

Give an example of A Priori justification.

Definitional truths, such as there are no married bachelors.

What does Hume suggest can only be justified A Priori?

Only relations of ideas, no matters of fact or real existence.

What does Empiricism suggest?

Any justified propositions concerning matters of fact are justifiable only on the basis of experience/a posteriori.

What is does Rationalism suggest?

Some justified propositions concerning matters of fact are justifiable by pure reason/a priori.

What is Hume’s question concerning propositional knowledge?

What is the nature of that evidence which assures us of any real existence and matter of fact beyond the present testimony of our senses, or the records of our memory?

What do we do we when Predict?

We use our knowledge of what sorts of effects the observed phenomenon tends to cause. Such as lightning causes thunder.

What do we do when we Retrodict?

We use our knowledge of what sorts of causes tend to bring about the observed effect. Such as a parking inspector caused a parking ticket on my car.

What is our knowledge of absent matters of fact based on?

Our knowledge of causal relations.

What does Hume suggest allows a priori justification?

If its negation is inconceivable/implies a contradiction. For example a bachelor who is married.

Can a proposition about causal relations be justified a priori?

No, because no proposition has negations that are inconceivable.

How do we get knowledge of causal relations?

We get it from experience. Not a priori because there are many conceivable effects for every cause.

What is an inductive inference?

Reasoning from a finite/limited set of observations for a broader conclusion. We make inductive inferences on past experiences.

Give an example for a Singular Inductive Inference.

1. Every F observed thus far is a G.

2. X is an F.

3. Therefore, X is a G.

Give an example of an Inductive Generalization.

1. Every F observed thus far is a G.

2. Therefore, all hitherto unobserved F’s are G’s.

What are our beliefs about absent matters of fact based on according to Hume?

They are based on our beliefs about cause and effect. They are formed via induction.

What does ‘cause and effect’ mean?

When we observe that A events are consistently followed by B events, we form the belief that this will continue to happen.

Define “Principle of the Uniformity of Nature”.

A necessary assumption that the future will conform to the past. This cannot be epistemically justified a priori or a posteriori.

Why can’t PUN be justified a priori?

Because we can coherently conceive of the world behaving radically differently in the future. A proposition is only justifiable this way if its denial is inconceivable.

Why can’t PUN be justified a posteriori?

Because the argument - on all past occasions I observed nature to be uniform, therefore, all occasions past or future, observed or unobserved, will be uniform - would have to engage in circular reasoning which is the logical fallacy of ‘begging the question’.

What does Hume believe we must be able to show if inductive inferences are rational?

That we have good reason to believe the future will resemble the past.

What is Hume’s argument against induction?

1. Induction is justified only if PUN is justified.

2. If PUN is justified then either it is justified a priori or a posteriori.

3. PUN is not justified a priori.

4. PUN is not justified a posteriori.

5. PUN is not justified.

6. Therefore, induction is not justified.

Why does Hume suggest we form epistemically unjustified beliefs?

The principle is Custom or Habit; makes inductive inferences innate with a genetic basis shaped by evolution.

Why is Hume called a ‘sceptic’?

Because he denies we have knowledge about absent matters of fact. Though he thinks they are unjustified, he also thinks it is good we make them.

Why does Hume seem more like an irrationalist?

Reason can’t give us knowledge, but we do have knowledge, so much the worse for reason.

What is one response to Hume’s irrationalism?

Maybe observations about constant conjunctions don’t justify a conclusion. But surely it justifies a probable conclusion; i.e., A will probably be followed by B.

Give an example of an inductive argument against Hume.

1. All past lightning flashes observed were followed by thunder.

2. So, probably every lightning flash is followed by thunder.

3. So, each hitherto unobserved lightning flash is such that it probably is/was/will be followed by thunder.

What is Salmon’s response to the probabilist reply?

What concept of probability are we operating with? What exactly does ‘probably’ mean? Salmon says we’re forced to assume PUN regardless of; a) Frequency, b) Degree of Rational Confidence.

Give an example of the Frequentist version of probablity.

If there were an infinity of die rolls, most rolls would in fact land on a face higher than 1.

Give an example of the Rational Confidence version of probability.

It is rational to have 83% confidence that this particular roll of the die will land on a face higher than 1.

Give an example of the Frequentist version of induction.

1. Every past flash of lightning was followed by thunder

2. So, if there were an infinity of lightning flashes, most of those would in fact be followed by thunder.

Problem: this still relies on PUN - why is 1 a guide to 2?

Give an example of the Rational Confidence version of induction.

1. Every past flash of lightning was followed by thunder

2. So, it is rational to have a high degree of confidence in the belief that the next flash of lightning will be followed by thunder.

Problem: also still relies on PUN