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Hume's new account of causality

In considering Hume's account of the origin of the idea of 'necessary connection' we have already collected most of the elements in Hume's positive account of causality. In giving his positive account of causality, Hume replaces necessary connection by the doctrine that events of type A are constantly conjoined with events of type B. The conditions that the cause must preceed the effect, and that causes and effects must be contiguous in space and time are retained. So Hume's positive account of causality is this.

We can legitimately say that A causes B if and only if:

  1. A preceeds B in time.
  2. A and B are contiguous in space and time.
  3. Events of type A are constantly conjoined with events of type B.

It is rather likely that as an account of the necessary and sufficient conditions for causality Hume's account is not satisfactory. On the other hand, as a psychological account of how we come to believe that A causes B, it may do better. Given the way Hume talks, it may not be unreasonable to take it in this way, rather than as a straightforeward definition of causality. Having now grasped Hume's revolutionary account of causality, we can now turn to his discovery of one of the great problems in philosophy -- the problem of induction.

What Is The Problem Of Induction?

Hume raises the problem of induction by noting that we have no problem with matters of fact of which we are presently aware or which our memory may tell us about. But this is a rather limitied sphere. What about things of which we are not presently aware. Does Australia exist -- even though I am not presently aware of any part of it? Surely it does, but what justifies my confidence in this claim? Will copper conduct heat tomorrow, or bread nourish me? Surely they will. But why am I justified in holding that these things are true. As Hume puts it:

Pg. 323 "It may therefore be a subject worthy of curiosity, to enquire 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."

Hume claims that all reasoning concerning matters of fact is based on cause and effect. (Pg. 323) So, how do we know that cause and effect claims about things of which we are not presently aware or assured of by memory are in fact true? The answer is that we constantly suppose that there is a relation between the present fact and that which is inferred from it.

Inferences from Present to Inferred Facts
Present fact: Inferred fact:
1. a letter, or knowledge of purposesthat his friend is in the country or in France
2. finding a watch or a machine in a desert that there had once been men in that island
3. the hearing in the dark of an articulate voice. the presence of some person engaged in rational discourse.

Cause/effect relations are discovered entirely by experience and not a priori. (Pp. 324-5) Hume established this claim in his account of causality which we have just finished exploring. The significance of this point for the problem of justifying inductive inferences will emerge shortly.

 

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