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David Hume

Hume, HobNobs and Metaphysics

Sally Latham shows how Hume’s views on causality really take the biscuit.

Hume is usually seen as the champion of the anti-metaphysical stance. In Section I of An Enquiry Concerning Human Understanding he says metaphysics is “not properly a science,” and seeks to “penetrate into subjects utterly inaccessible to the understanding” (p.11, OUP edition). In particular, the usual understanding of Hume concerning causation is that he claimed any reference to causes – metaphysical bonds between events, or some sort of mysterious power rendering one event the necessary consequence of another – is not rooted in experience, and hence meaningless. Rather, what is derived from experience is a ‘constant conjunction of events’. Through habit we begin to form expectations about one event following another, and so derive the idea of cause: cause must be defined as regularity and expectation, nothing more. Eating a whole packet of HobNob biscuits has been constantly conjoined with my feeling a little sick, and so I expect to feel a little sick next time I eat a whole packet of HobNobs. To Hume this is all that is meant by the claim that eating a whole packet of HobNobs causes me to feel a little sick.

For Hume, a belief in cause and effect is central to our psychological development, and allows us to make assumptions beyond that which is happening at this very moment. In other words, after a number of such instances, it allows me to move from the occurrence of eating a whole packet of HobNobs being followed by feeling a little sick, to the belief that in the future, eating a packet of HobNobs will again cause me to feel a little sick (and perhaps I will now avoid doing it).

This places ideas about causation firmly in the realm of what can be experienced. Hume’s Theory of Ideas states in no uncertain terms that we have no genuine concepts that cannot be traced in some way to impressions (experiences). Causal powers are not something we can have a meaningful idea of, then, as they fall neither in Hume’s realm of ‘relations of ideas’ – propositions that can be reasoned about – nor of ‘matters of fact’ – propositions that can be experienced with the senses – and all ideas can only be formed in these two ways for Hume. As beliefs are ideas, we can’t believe in causal powers either, only in regularity. No experience means no idea, and no idea means no belief.

Old Hume vs New Hume

Anthony Quinton wrote that Hume’s account of cause and effect is “rightly, the best known and most influential part of his philosophy” (The Great Philosophers – Hume, 1998), yet there is some debate as to what exactly he meant. The ‘New Hume Debate’ concerns how we should interpret Hume’s stance on causation and any supposed ‘causal powers’ connecting events. Somewhat surprisingly, Hume has been accused of making metaphysical claims.

The old interpretation of Hume, known as ‘Old Hume’, states that Hume claimed that we should not believe in any causal powers (see Popkin, The High Road to Pyrrhonism, 1980), or even more extreme, that Hume was stating that there are no causal powers. The ‘New Hume’ approach, taken by Professor Peter Strawson amongst others, states instead that Hume believed that causal powers exist even if we cannot know them.

The problem is that Hume seemed to be making contradictory claims in theEnquiry:

1. We should believe in ‘cause’ in some sense, or we will be stuck with only what is directly present to the senses, and can form no beliefs about the future. Even children, animals and ignorant peasants (Hume’s words) form such beliefs in order to function successfully: “By means of this relation alone can we go beyond the evidence of our memory and senses.” (Section IV)

2. We can’t have beliefs not grounded in sense experience: “It is impossible for us to think of anything, which we have not antecedently felt, either by our internal or external senses.” (Section VII)

3. We do not have any sense experience of causal powers: “When we look around towards external objects… we are never able, in any single instance, to discover any power or necessary connexion, any quality which binds the effect to the cause, and renders the one an infallible consequence of the other.” (Section VII)

Putting (1), (2) and (3) together, Hume seems to be saying that we think in terms of causes, yet it is impossible to do so.

There have been philosophers who have rejected each of these points in an attempt to interpret Hume consistently. The Old Humeans would reject point (1), at least in the sense of rejecting belief in cause being any sort of belief in causal power, and instead stick firmly to the ‘regularity’ thesis, that ‘As cause Bs’ means As are constantly conjoined with Bs, and we expect Bs when presented with As. We may project some mysterious metaphysical power bonding the events, but this is something we invent, then impose on the events. The events themselves do not show such powers. Nothing in A makes B necessary.

A problem with the regularity thesis is that it seems to result in absurd conclusions. Suppose that I am a very predictable person who loves routine. I come home from work every evening at the same time exactly, make a cup of tea and fetch a HobNob before settling down to watch Neighbours repeats. I like to begin to eat my HobNob just before the theme music starts. This happens day after day, resulting in a regular conjunction of biting into my HobNob and Neighbours starting. But surely it would be a mistake to say that my HobNob eating was the cause of Neighbours starting?

Heroic Hume vs Agnostic Hume

There are Old Humeans who would bite the bullet on this, and claim that since cause is no more nor less than constant conjunction, so, yes, ‘cause’ is what we have in the HobNobs and Neighbours case. This view is known as ‘Heroic Hume’, and is consistent with what he writes, if somewhat extreme. Consistent, yes, but the idea does seem a tad counterintuitive.

A different problem comes if we take the view that Hume claimed that causal powers do not exist. Although at first this might seem to be a simple anti-metaphysical, empiricist claim, it is not. As Strawson points out, claiming that causal powers don’t exist is itself a metaphysical, and so to Hume unverifiable, claim about the way the world is, and so would not be consistent with Hume’s statement that we shouldn’t be speculating about things not grounded in sense experience.

As far as rejecting Hume’s point (2) goes – the claim that beliefs must be grounded in sense experience – suffice to say that most scholars think Hume stood firmly by his Theory of Ideas, ie, that all ideas are the result of preceding impressions.

Craig, a New Humean, suggested that we should reject point (2), claiming that Hume wasn’t all that hung up on the Theory of Ideas, and later rejected it (The Mind of God and the Works of Man, 1987, p.120). This seems somewhat implausible, given the fact that the Theory was the cornerstone of Hume’s empiricism and that he was so keen to keep this principle throughout his work.

So for a consistent reading of Hume, this leaves the rejection or modification of point (3), the point that we do not have any experience of causal powers.

The more common New Hume interpretation, proposed by Strawson amongst others, is that Hume says that we cannot know what causal powers are, but that he believes they exist. There is something that makes the world regular, but what it is is not knowable to us. In this sense, Strawson is claiming that Hume is a realist about the fact that causal powers exist, but an agnostic about what they actually are.

In The Secret Connexion: Causation, Realism and David Hume (1989), Strawson accuses the Old Humeans of confusing (E), the epistemological claim that all we can know about causation, is regularity, with (O), the ontological claim, that all that causation is, is regularity. Strawson further claims that a strict empiricism (such as Hume followed) requires that (E) implies a semantic claim, (S), that all we can meaningfully say about cause, is that it is regular succession. Strawson says that the Old Humeans move from (E) to (S), and then illegitimately from (S) to (O). Strawson not only questions the legitimacy of this move, but also the conclusion (O), as claim (O) is itself metaphysical, and so at odds with Hume’s general empiricism.

Strawson also looks at Hume’s usage of the term ‘unintelligible’ in reference to causal powers. He says we don’t have to take this as meaning that the idea of causal power is useless and should be discarded, but rather that it is unintelligible in Locke’s sense of the unintelligibility of the essence of gold. The essence of gold, Locke said, was unknowable to us; but we can still assume that gold does have an essence, and we can still talk about it. In the same way, to Hume the nature of cause is unintelligible to us, and we will probably never understand it, but we can assume the existence of causation, and discuss it.

This leaves us with the problem of how we can conceive of something we have no impression of. Here Strawson comes to the rescue by making the distinction between ‘supposing’ and ‘conceiving’. To conceive, says Strawson, is to be aware of a certain idea or mental image. Yet to suppose is a relative idea, lacking any images or specifics. Say for example I am in an empty house, and I leave my cup of tea and pack of HobNob biscuits on the desk while I go into another room. When I come back my cup is empty and my biscuits gone. I have no idea what has caused the disappearance of my tea and HobNobs. I do not know the cause. Yet I can suppose some cause to have occurred, even if I cannot conceive what it is or might be. In the same way, Strawson claims that we can suppose that causal powers exist without conceiving precisely what they are. This move involves a broader understanding of the Theory of Ideas, not a rejection of it. What seems to be disputed here is the doctrine that any idea not firmly rooted in impressions is meaningless.

Yet this does not seem to avoid metaphysical speculation, which would make it a problem for Hume. The supposition of unknown causal powers assumes that events do have a cause, even if we cannot conceive what the cause is. This is not consistent with Hume’s claim that we cannot know anything about cause. The problem for Hume here is that the claim ‘all events can be supposed to have a cause’ is itself not rooted in impressions, and is therefore only meaningless metaphysical speculation. There is nothing in my experience to say that the disappearance of my tea and HobNobs had a cause, for instance.

One troublesome matter for the Old Hume interpretation – that Hume says we should not believe in causes – is Hume’s reference to ‘secret causal powers’. Take for example Enquiry Section VII, when he’s talking of the times when medicines do not work as we expect them to, or when irregular events follow from regular ones. He says, “the philosopher and physician are not surprised at the matter, nor ever tempted to deny, in general, the necessity and uniformity of those principles by which the animal economy is conducted.” He goes on to add that “many secret powers” lurk in the human body that are beyond our comprehension. This seems to back up Strawson’s New interpretation, of Hume as positing real but unknown causes, as illustrated with the example of gold. But the Old Humean does have a reply: such ‘secret powers’ are not metaphysical ‘causal powers’ to Hume, but rather regular connections that have not yet been discovered by science. Physics will reveal regular connections that we are now ignorant of, but never causal powers.

Humean Responses

There are ways for both Old and New Humeans to answer critics. The Old Humean could see the claims Hume makes about causes not as about what is actually the case in the world, but as semantic claims, about what we can meaningfully discuss or conceive. Thus Hume’s ideas about causation are not referring to what is the case, but what we can actually think about it. We cannot conceive of causal powers, as we have no experience from which to form an idea of them. We may persist in talking about them, but our language is confused, at best. The New Humean can interpret Hume as saying that we don’t know that there are causal powers at all, never mind their true nature – we just believe there are some. This agnostic metaphysical claim has no metaphysical ramifications.

An alternative approach has been offered by Daniel O’Brien and Alan Bailey in Hume’s Enquiry Concerning Human Understanding – A Reader’s Guide (2006). This they term ‘Modified New Hume’, and it allows what seems to be a consistent reading of Hume. Modified New Hume simply states that Hume left the question open: it is possible that there are causal powers – no more and no less. To confirm or deny the existence of these powers underpinning our universe would be to make a metaphysical claim, much like confirming or denying the existence of a material world. Instead, we are left with a consistent, unmetaphysical, ‘maybe’. Did the disappearance of my HobNobs have any sort of cause? Perhaps… perhaps not. We really couldn’t say.

I cannot help thinking though, that we have had to work hard to find a consistent reading of Hume on causation, and that he could have made life a little easier for his defenders.

Sally Latham is a philosophy lecturer at Birmingham Metropolitan College, and new mum to Charlie Latham.

• With many thanks to Dan O’Brien for help, advice and patience.