Critically discuss the adequacy of Hume’s constant conjunction thesis as an analysis of cause and effect.
David Hume was an empiricist because he believed that nearly all our knowledge derives from experience. (Except for what he calls “relations of ideas”, such as the truths of geometry and arithmetic but has little to say about them)
Hume does not only argue that our ideas derive from impressions i.e. sensory and emotional experiences but that the connections we make between ideas also derive from experience.
Principally the most important “principle of connexion” between ideas is the notion of cause and effect. He believed that our knowledge of cause and effect is entirely derived from sense experience. Furthermore when we know that something is closely linked to something else.
Hume’s constant conjunction thesis is the view that one event follows another. In other words, A is always followed by B. Hume gives the example that when you eat bread you know that it will be followed by the bread nourishing you. But at no stage can we observe the process / development. In other words, we can’t observe something making something else happen.
He pointed out that we proportion our belief that something is the case to the evidence we have for it and that the only way we learn about A following B / cause and effect is through experience.
In section IV of the Enquiry, Hume affirms this as a general principle. Knowledge of the connection of one phenomenon with another arises purely from experience .It cannot, as Hume puts it, be known a priori, before and independently of all experience. He uses the example of Adam, he could not known prior to further experience, that water is fluid and transparent and that it possessed the power to drown and suffocate him and also not only with water but for example if Adam was to encounter a fire he could not logically deduce that the warmth and light of the fire consequently would burn him. That would have to be revealed by experience alone to him. Moreover Hume also claims that things have what he calls “secret powers” and that you cannot know the secret powers of things prior to experience.
In everyday life we experience cause and effect, for example, when a child has a wound, let’s say in his leg, we know the effect it’s going to have, and that is that the child will feel pain. Hume claims that cause and effect cover everything of the association of ideas. In other words, that in some way our ideas follow a sequence/ chain. One thing follows another in some kind of order and direction.
Why can’t we work out the effect from seeing the cause? According to Hume we can only know the effect of something by experience only and can’t be worked out beforehand. He claims that by using reason i.e. the mind, that it can never possibly find the effect of the supposed cause even if examined.
He held that we can discover the causes of things to a certain extent, but the discovery of the ultimate causes of things is something which will for ever elude us.
Hume also challenges the reader and asks; if there is anything a priori what is it then? It seems quite complicated to think of something we could know a priori.
So it seems that cause and effect as Hume proposes can only be known thorough experience only and that even though we experience A causing B , all we have actually observed is the constant conjunction of A and B- an from this we assume A caused B. But this tends to be in some way an association of ideas and not something that we can prove to exist in this world.
Hume’s big question then is how do we know the future will resemble the past? He used the bread example to illustrate the problem. As we eat bread and know that it is nourishing us, how do we know next time it would do the same thing? We don’t really, we just make an assumption that it will but it doesn’t mean is going to happen.
Cause and effect as we have seen offers no guarantee that the future will resemble the past. Nevertheless our belief in cause and effect, is not rational, but an instinct to accept custom as a guide to the future. Even though Hume is a sceptic he doesn’t live his life as one. Like everyone he does assume cause and effect is true and that you can trust it but as a philosopher he is able to arise these doubts. Furthermore he claimed that when we see something happening once and assume it will happen again it is down to psychology and not logic.
Karl Popper agreed with Hume’s explanation of cause and effect. He describes it as clear and conclusive. Nevertheless he did feel Hume’s psychological explanation of induction (the future resembling the past) in terms of custom or habit was poor. Hume’s psychological theory is one of repetition, based on resemblance or similarity that when we see something happening once we assume it will happen again. The kind of repetition pictured by Hume can never be perfect. As Popper points out, the cases he has in mind cannot be cases of perfect sameness but only of similarity. Thus they are repetitions only from a certain point of view.
In other words, ( what I think Popper is trying to say but I’m not sure) instead of waiting for repetitions or regularities to form some kind of pattern that we can all agree and follow we keenly impose our own regularities upon the world without constructing solid premises thereby jumping to conclusions. Being a theory of trial and error these conclusions can later be proved wrong.
The big problem is the lack of description about the secret powers of things; the only thing we are told is that they’re unknown to us. This may well be the missing piece of the puzzle. If we were to know the secret powers of things maybe it would help us to understand more about cause and effect.