by HELEN BEEBEE
Hume’s account of causation has a good claim to being one of the most influential views in the history of philosophy. It not only set much of the agenda for large swathes of analytic philosophy in the 20th century and beyond, but it also awoke Immanuel Kant from his “dogmatic slumber” – as he put it in his Prolegomena to any Future Metaphysics – and prompted him to write the mighty Critique of Pure Reason, itself a hugely influential work and arguably the starting-point for the continental tradition in philosophy.
So why has Hume’s view on causation proved to be so influential? Well, let’s start with the state of play in philosophy at the time Hume was writing. The dominant view of causation at the time was a part of what Edward Craig (in The Mind of God and the Works of Man calls the “Image of God doctrine”. The idea here is, as the name suggests, that we are made in God’s image: our mental faculties are of course rather feeble compared to God’s, but they are of the same kind as God’s. If you were in the grip of the Image of God doctrine, you might think something like this. Our mental faculties are at their most perfect – their most God-like – when we’re engaged in a priori reasoning, for example when we’re constructing a mathematical proof. And in a mathematical proof, we can (if we’re really good at maths) just “see” or “intuit” that each successive stage of the proof follows from, or is entailed by, the preceding stage. So, if our mental faculties generally are God-like, then the same kind of thing must be going on when we turn our attention to the causal structure of the world. At least in principle, if I look at some event – the cue ball hitting the black ball in snooker, say – I can tell, just by observing that event, what must happen next: I can infer, on the basis of just that experience, what the collision will cause, just as I can in principle tell just by looking at a mathematical theorem what follows from it.
Hume’s fundamental insight when it comes to causation is that that story cannot possibly be right. No matter how hard I look, and no matter how much I know about the size and shape and weight of the balls and their position on the table, nothing whatsoever follows about what the collision is going to cause. Of course, what I expect to happen is that the black ball will move off in a certain direction and (let’s suppose) land in the corner pocket. But that is not something I can deduce just from careful observation of the collision. As Hume puts it: “If we reason a priori, any thing may appear able to produce anything”.
A crucial – and perhaps the most influential – part of Hume’s argument is that we cannot observe the causal relation itself. When I look at the snooker table, all I see is the cue ball hitting the black ball, followed by the black ball moving off: I don’t see any “necessary connection” between the two. Because I have frequently seen this conjunction of events before, I come to expect the black ball to move – but this expectation is generated not by any kind of a priori inference. Rather, it is generated by “habit or custom”: we are endowed with a kind of instinct that prompts us to expect, on the basis of past “constant conjunctions”, that the same thing will happen this time. It is this insight – coupled with the empiricist thought that all of our “ideas” or concepts must be based on experience – that led analytic philosophers to go in one of two directions.
First, many philosophers in the empiricist tradition (itself traceable to the three great “British Empiricists”, of whom Hume was the third, after Locke and Berkeley) came to regard “causation” as an illegitimate pseudo-concept. Since we cannot trace our idea of causation to some observable feature of reality, we really don’t mean anything at all when we say that one thing caused something else. Thus we should shun causal talk all together. This was a dominant view in analytic philosophy until quite late in the 20th century. Russell famously quipped that “the law of causality” was “a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm”, and Peter van Inwagen said of “cause” that it is a “horrible little word”.
Second, some philosophers took the view that causation just is a matter of constant conjunction: all we mean when we say “the short circuit caused the fire” or “touching the hot iron caused me to feel pain” is just that the former kind of event is always followed by the latter kind. Unfortunately, this view as it stands is clearly hopeless. (Imagine that when I flip a switch, two lights – A and B – go on, one just after the other. The illumination of A is constantly conjoined with the illumination of B, but of course the former is not a cause of the latter; rather, they are both common effects of my flipping the switch.) But most of the major theories of causation that were developed in the latter part of the 20th century retain the guiding thought that causation reduces to regularity – they just make the story much more complicated in order to avoid this kind of counter-example. Statistical relevance theories, John Mackie’s INUS condition account, and David Lewis’s counterfactual theory all belong in this category.
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