Book 1, Part III:  Causal Inference



Section 1.  Knowledge [= Science] is certain.


Knowledge comes from Reason alone.  The objects of knowledge can be known with certainty.

Four relations that can be known with certainty:  resemblance, contrariety, degrees in quality, and proportions in quantity or number.

[Hume discusses certainty in T1.3.3.2.]


Three relations that cannot be known with certainty, because they depend on experience:  contiguity in time and space, identity, and causation.


Two modes of knowledge:  Intuition and demonstration.


Knowledge of relations that depend entirely on the ideas.  Includes algebra and arithmetic, but not geometry.  Why not geometry?  [Like Kant, Hume thought that diagrams were an essential part of geometric reasoning.]


What is the source of mathematical and geometric ideas?








Section 2.  Belief is probable. 


Probable belief of contingent relations.  


Probable belief depends on experience.  Three contingent relations:  identity, contiguity in time and place, and causation.


Only causal reasoning can take us beyond present impressions.  Why?  If we infer identity over time or contiguity in space over time, the inference is causal.  Why?



The Idea of Causation.


Is it a simple idea?  How does Hume show that it is not?


So it is a complex idea.  In this section Hume identifies three simpler ideas as elements of the complex idea:  (1) the idea of contiguity in time and space [this seems like two ideas]; (2) the idea of temporal priority; and (3) the idea of necessary connection. 


(1) contiguity in time and space:  Causes must be temporally and spatially contiguous to their effects [No action at a distance.]


(2) temporal priority [succession].  What is Hume’s argument for this condition.  




(3) What is the source of the idea of a necessary connection?

        Hume considers the possibility that the idea of cause is an exception to the Copy Principle.  However, he asks us to wait until he has fully explained causal inference.  He will explain the idea of necessary connection on the basis of his explanation of causal inference.























Section 3.  The Principle of Universal Causation: 

Whatever begins to exist has a cause of its existence.


Hume’s goal is to show that the principle could not be known with certainty by reason.


First, it is not intuitively certain.


Second, it cannot be demonstrated from what is intuitively certain.


What is Hume’s argument?  It depends on the imagination.  How would an opponent reply?


What does Hume say about the following proposition:

Every effect has a cause?
















Section 4.  Causal reasoning:  reasoning concerning cause and effect.


How can the mind reason about cause and effect, if causes cannot be determined by Reason?


To maintain the distinction between knowledge and belief, we will distinguish Reasoning [with a capital ‘R’] from reasoning [with a small ‘r’].


Causal reasoning depends on impressions or “ideas of memory, which are equivalent to impressions”[T].


Kinds of causal reasoning:


(1) from a cause to an effect.


The example of our knowledge of the death of Caesar.














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


Note:  We can use coherence considerations to determine what is true and false.  Impressions and memories cohere together.  This is the basis of causal inference.


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.)


It is also the solution to the distinction between belief and imagination.  Force and liveliness.

















Section 6.  Causal inference:  from a cause (impression of sensation or memory) to an effect (idea). 


Why can causal relations not be known intuitively?


What is the alternative?


Key:  "the necessary connection depends on the inference, instead of the inference's depending on the necessary connection"[T]  It will not be until the end of section 8 that we will be able to explain what he means.


The example of flame and heat.


What do we observe?  (1) contiguity in time and space; (2) temporal  priority; and a new element:  (3) constant conjunction [in the past].


The problem:  How to infer a future effect from a present cause on the basis of (1)-(3).


Could causal relations be known deductively?


Answer:  Yes, if Reason could produce the missing premise:  (UN = Uniformity of Nature) “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”[T]


Could this premise be known intuitively?  Deductively?

What is the only alternative?

That UC is the result of causal reasoning!  But then causal reasoning would be circular.  Consider the following argument:




Premise:  In the past, like causes have produced like effects.


Missing Premise:



Conclusion:  (UN) In the future, like causes will produce like effects.


What is the missing premise?
















The solution to the explanation of causal inference:


It is not a form of Reasoning [with a capital ‘R’], but of reasoning [with a small ‘r’]in which imagination takes us from the idea of the cause to the idea of the effect by a principle of transition from impressions (including “impressions” of memory) to belief.


What example does Hume use to illustrate the transition? 


What is the principle that explains the transition?  Hume will answer that question in the next section.




















Section 7.  Belief


Knowledge is certain.  It carries absolute necessity.

The negation of knowledge is absurd.  It cannot even be thought.

[Is this true?]


Belief concerns what is contingent. [Neither it nor its negation are necessary.]


The difference between belief and incredulity in an idea is the manner of our conceiving the idea.


Three Accounts of Belief = (1) lively idea related or associated with a present impression (including the “impressions” of memory).

        (2) lively idea produc’d by a relation to a present impression (including “impressions” of memory)

        (3) an idea + a feeling


The feeling gives beliefs “more force and influence; makes them appear of greater importance; infixes them in the mind; and renders then the governing principles of all our actions” [T]


Hume tests his account by comparing history with literature.  Is what he says about them true?




What explains the transition from cause to effect?  “Custom or a principle of association”[T]


Note:  In footnote 20 on p. 67, Hume acknowledges that causal reasoning can go in reverse, from the effect to the cause.  How would that be possible on Hume’s account?


























Section 8.  The Causes of Belief


The Transmission Principle [Hume’s second causal principle]:  “When any impression becomes present to us, it not only transports the mind to such ideas as are related to it, but likewise communicates to them a share of its force and vivacity”[T1.3.8.2]


The three kinds of transition:


(1) resemblance:  the example of the photo of a friend.


(2) contiguity in time and space:  thinking of home.


(3) causation. 
















How can an impression of a cause lead us to infer its effect?


What is responsible for the transition?  Custom.


“Thus all probable reasoning [with a small ‘r’] is nothing but a species of sensation”[T]  What does Hume mean? 


In paragraph 13, Hume explains how memory can be involved in causal reasoning without our being aware of it—by “secret operation, without being once thought of”.


IMPORTANT QUESTION:  Call causes of which we are not aware, hidden causes. A secret operation would involve a hidden cause.  On Hume’s account of causal reasoning, could we ever come to believe in a hidden cause?


Paragraph 14:  What is Hume’s explanation of inference from a single case?


Paragraphs 15-16:  Hume explains how we can have the memory of having an idea. What is the puzzle that he is trying to solve?  What is the solution (i.e., what does he mean by “that certain je ne scai-quoi”(T


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.