Causality

Bertrand Russell famously claimed that:

The law of causality, I believe, like much that passes muster among philosophers, is a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm.

Russell seems to have thought himself to be reporting a widespread attitude among natural scientists, especially physicists. We doubt that he was correct about that. But in any case, something like Russell’s view has been quite popular among (analytic) philosophers — from the 1950s and until today. Indeed, these philosophers believe themselves to be carrying forward the austere program of David Hume.

As usual, it’s not completely straightforward to figure out Niels Bohr’s views on a philosophical topic. He rarely states his views directly, much less argues for them. What’s more, Bohr bends his philosophical views in reaction to developments in his scientific practice. Bohr’s views about causality offer an extreme example of his philosophical flexibility. At times he insists that the principle of causality must be maintained; and at other times he insists that we have no reason to think that nature will comply with our apriori principles of intelligibility.

Hume and Kant

David Hume famously criticized the traditional view about causes in nature and our knowledge of them. This traditional view has two components, one metaphysical, and one epistemological. The metaphysical component says that there is a relation between events where the former causes or brings about the latter. For example, we would tend to think that a rock striking a thin window pane causes that window pane to break. Similarly, we tend to think that a person’s recovering from strep throat is caused by their taking penicillin.

The traditional view also has an epistemic component, namely that humans are capable — somehow or other — of coming to know that one thing causes another. Perhaps we get to know that one thing causes another after seeing a single instance, or perhaps it takes our seeing many instances. Details aside, the important fact is that somehow or other, human beings are able to know fairly reliably that one kind of event causes another kind of event.

We won’t review here the elements of Hume’s critique. What’s important for us is tha Hume convinced himself that the traditional view of causality is untenable. What’s more, Kant was convinced that knowledge of nature is possible only if we know about cause-effect relations, and so he thought that something must go wrong with Hume’s argument.

Historians of philosophy disagree about whether Hume himself had a ‘solution’ to his argument against causality. It was rather popular in the late 20th century to see Hume as proposing an “empiricist acceptable” analysis of the cause-effect relation. The idea here is that Hume is willing to give up the metaphysical component of the traditional view – i.e. that there is some “thick” relation (as suggested by “bringing about”) – in order to save the fact that we can know that one event causes another. In short, if one can show that “x causes y” can be cashed out in terms of facts to which we clearly do have empirical access, then our knowledge of causal relations can be saved.

Høffding’s views on causality