Book 1, Part III: Causal Inference

Section 1. Knowledge

Knowledge of relations that depend entirely on the ideas. Knowledge comes from Reason alone. Includes algebra and arithmetic, but not geometry. Why not geometry?

Hume discusses certainty in T1.3.3.2.

Section 2. Probable belief of contingent relations.

Probable belief depends on experience. Only causal reasoning can take us beyond present impressions.

And the Idea of Cause and Effect.

The three external elements of the relation of cause and effect: (1) contiguity; (2) temporal priority; (3) constant conjunction.

What is the source of the idea of a necessary connection?

Hume is not ready to answer this question until he has fully explained causal inference. He will explain causal necessary in terms of causal inference.

Section 3. Reason cannot establish that whatever begins to exist has a cause of its existence.

Section 4. How probable belief is established by chains of cause and effect.

Note that ideas of memory are "equivalent to impressions."

Section 5. The role perceptions and memory in causal reasoning.

Note: We can use coherence considerations to determine what is true and false.

What is the difference between ideas of memory and ideas of the imagination?

The key idea: there is a difference in feeling. (This is the clue to solving the problem of necessity.)

Section 6. Causal inference. The inference from the impression of a cause to the idea of its effect.

Why it cannot be an inference of Reason.

What is the alternative?

The example of flame and heat.

Key: "the necessary connection depends on the inference, instead of the inference's depending on the necessary connection." What does this mean?

Reason cannot be the source of causal reasoning. Causal reasoning is not demonstrative.

Causal inference is the result of a union of ideas in the imagination. It is a kind of custom or intellectual habit. What example does Hume use to illustrate this sort of habit?

Section 7. Belief

Knowledge carries absolute necessity.

Probable belief = a lively idea related to or associated with a present impression.

Belief in existence is the result of causal reasoning. It is the result of custom or an intellectual habit. See note 20 for more on the nature and importance of causal reasoning.

Belief is an idea with superior "force, or vivacity, or solidity, or firmness, or steadiness." All of these terms refer to a feeling.

Belief is either the direct result of impressions or it is the result of associations of ideas in imagination, of which the most important are causal associations.

Section 8. The Pathways to Belief

Three principles of association of ideas can transmit force and vivacity from an impression to an idea: resemblance, contiguity, and cause and effect.

What does Hume mean by "all probable reasoning is nothing but a species of sensation."(T 1.3.8.12)?

In paragraph 13, Hume explains causal reasoning as a kind of unconscious inference.

In paragraph 14, Hume explains causal inference on the basis of a single case.

At this point, Hume believes that he has fully explained causal inference. He is ready to return to the question of the source of the idea of necessary connection.

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