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Ockham, Hume & Epistemic Wisdom

William Grey launches an all-out attack on the paranormal armed with a couple of razors honed with the whetstone of scepticism.

‘Philosophy’ is a word taken from Greek, and literally means ‘love of wisdom’. But what is wisdom? I suggest that it is the capacity to make the most appropriate choices, or at least avoid the most serious pitfalls, from among the bewildering alternatives which confront us in the course of our lives. This can be clarified with the help of an analogy.

Imagine that you are lost in a maze. It would be of immense benefit to gain an overview of your predicament because that would help you to understand your position and thereby assist you to reach your destination. Wisdom is the capacity to articulate our situation constructively from a point of view which enables us to see consequences and identify irrelevancies more clearly, thereby empowering us to make better choices. A wise person is one who is able to provide such a perspective. Striving for wisdom is important because by widening our horizons we are able to see more clearly what the alternatives for living are.

This sort of wisdom is practical wisdom; that is, it attempts to provide an answer to the problem, raised long ago by Socrates (469-399 BC) about how one should live (Plato, Republic, 352D). We also seek wisdom when we try to deepen our understanding of what the world is like. Wisdom is bound up with an enrichment of our understanding of ourselves and our world, and how best to live in that world. How should we set about the task of becoming wise?

If we want a clear and accurate understanding of the world, we need to eliminate inconsistent beliefs. For example, to suppose that the earth is flat, or that a pure water diet will cure a viral infection, may have serious practical consequences for navigation or health. Evidence may mislead us seriously, or even fatally: it is usually important to be right.

Seeking rational principles for matching our beliefs to the available evidence is the province of the branch of philosophy called ‘epistemology’, which is concerned with the nature of knowledge and belief. Another important branch of philosophy relevant here is metaphysics, which tries to discover the basic structure of reality. The Cambridge philosopher C.D. Broad (1887-1971) pointed out that we habitually and unconsciously presuppose a number of metaphysical assumptions in interpreting our experience of the world. These assumptions, which Broad called basic limiting principles, include (1) a general principle of causation that future events can’t affect the present before they happen, that is, backward causation is forbidden; (2) that a person’s mind cannot directly produce changes in the external world without some intervening steps involving the person’s body; (3) mental experience is produced and conditioned by events in a brain, that is, disembodied spirits do not exist as persons separable from physical bodies; (4) knowledge and perception of remote events or objects is always conveyed by some causal chain connecting us to those spatially or temporally remote items. One corollary of this fourth principle is that we cannot know directly what happens at distant points in space and time without some sensory perception or energy of it being transmitted to us; another is that we cannot know the content of someone else’s mind except through inferences based on observations of their speech or behaviour, or more subtle physiological cues (Broad 1949, pp.293-296).

Suppose for example that some secret government (or industrial) information turns up in the possession of an adversary (or competitor). Few of us would consider the possibility that the information has been obtained through the services of a psychic sleuth. We tend to follow Broad’s basic limiting principles as a matter of course when dealing with practical matters.

Science provides strong support for each of Broad’s principles, and no one has provided any reliable, replicable evidence against any one of them. Yet each of these assumptions is called into question by so-called ‘paranormal’ claims. Paranormal claims therefore provide an interesting challenge to some of our central metaphysical assumptions about what the world is like, and also raise a basic problem about our knowledge of the world. If they are true, these claims would give us good reason to believe that in some important respects scientific knowledge is seriously incomplete or fundamentally mistaken.

Our problem is that we are told by some people (psychics and clairvoyants, for example) that we have good reason to believe that what science tells us about the world is wrong. And the scientists tell us that the pronouncements of the friends of the paranormal are a tissue of fantasy, error, wishful thinking and fraud.

We might hope that philosophy can say something useful in this sort of predicament, where we are confronted with conflicting testimony. The scientists might be wrong, or the psychics might be wrong; indeed they both might be wrong (though one side might be more wrong than the other). But they can’t both be right. Can we get an overview? A perspective which will help to throw some light on this conflict of claims?

The first point to note is the difference between doubt and disbelief. If someone presents what they believe to be compelling evidence that something extraordinary or counterintuitive will happen (say that it will snow in Brisbane next Christmas, or that plants grow better in strong magnetic fields), but I don’t believe the evidence is sufficient, I don’t have to conclude that it won’t snow, or that the plants won’t grow any better. I can just conclude that the evidence is not good enough, at this time, to settle the matter definitely either way. Scepticism is a matter of doubt rather than denial.

In fact this is the characteristic stance of scepticism. A sceptic is someone who calls a knowledge claim into question. Being sceptical – that is, withholding assent, or suspending belief in a particular claim – need not involve believing the opposite. Scepticism is dogmatic when assent is withheld on the basis of prior conviction without considering the evidence. Scepticism is global if it encompasses all claims to knowledge; selective if it is directed at specific knowledge claims. Global scepticism is rare outside philosophy seminars. Dogmatic scepticism, regrettably, is less unusual.

Many of our beliefs, such as those about the content and composition of our immediate surroundings, are relatively immune to sceptical doubts. You don’t doubt the existence of chairs and tables, or the paper on which these words are written. Other claims (such as those which concern tooth fairies and Santa Claus) we dismiss immediately. Between these extremes lie disputed cases, such as God or economic rationalism – and also psychic and paranormal phenomena.

Scepticism of course is not the same as cynicism – though cynicism is a form of scepticism, namely scepticism about the sincerity or goodness of human motives and actions.

The undogmatic variety of scepticism, called critical scepticism, means keeping an open mind and not rejecting disputed claims without examining the facts. It involves refusing to accept as true claims for which there is insufficient or ambiguous evidence, and recognising that withholding belief is preferable to accepting claims for which there are not sufficient grounds. Scepticism is all about matching belief to evidence. It adopts a methodological maxim that in seeking explanations we should prefer the ordinary to the extraordinary, and the simple to the complex. This maxim is sometimes identified with a principle attributed to William of Ockham (1285-1349), and called ‘Ockham’s Razor’.

There are some surprising and interesting parallels between the structure of scientific explanation and the structure of psychic explanations which cannot be explored here. Instead I’m going to sketch the wisdom of the Scottish sceptical philosopher, David Hume (1711-1776), who addressed, more than two centuries ago, a problem which is a precise analogue of the problem which paranormal claims raise for us now. This is a case in which the argument of an illustrious figure in the history of philosophy has important relevance for us today.

What should we do when confronted with claims which are conspicuously at odds with the general run of experience? That’s the problem which the paranormal presents for us, and it’s the problem which miracles presented for Hume. Paranormal phenomena are events which appear to be quite astonishing – frequently at odds with well-established laws of nature. And the violation of a law of nature is Hume’s definition of a miracle.

After looking at the credentials for miraculous claims, Hume came to the conclusion that the balance of probabilities counted against them. Hume was aware of the impossibility of proving a negative: there is no way that he could prove that miracles never happen. But he developed an ingenious argument to show something a little different, which would be of considerable consequence: that is, that it is never rational to believe that miracles have occurred. Hume was concerned, that is, with an epistemological question of what it is and is not rational to believe, rather than a metaphysical argument about what sorts of events are possible in our sort of world.

Hume’s argument has two stages. First he argues that the evidence against miracles is usually very strong. In arguing for this, Hume proposes a principle which has been called Hume’s Razor:

No testimony is sufficient to establish a miracle unless that testimony be of such a kind that its falsehood would be more miraculous than the fact which it endeavours to establish. (‘Of Miracles’, pp.115-116)

Hume here argues that if we are asked to believe something which appears to be extremely improbable, we should ask which is more likely: that the improbable event happened, or that the testimony supporting this improbable event is mistaken. Only when the falsehood of the evidence is less credible than the truth of the miraculous claim can we accept the evidence as warranting belief in the contested event. In practice, Hume said, no miracle satisfies this reasonable standard of evidence, and therefore there is no miraculous claim proven beyond reasonable doubt. This is a basic ground rule in scientific practice: extraordinary claims must be backed by extraordinary evidence. The fiasco about ‘cold fusion’ initiated by Pons and Fleischman provides a recent illustration of the failure to supply sufficient evidence for an extraordinary claim. There are of course cases in which surprising claims have been substantiated and through this process anomaly becomes naturalised. This is an important way by which human knowledge is extended. However, our understanding is enriched by deepening our understanding of the laws of nature rather than by discovering miraculous exceptions to them.

Though the standard of evidence we demand to substantiate extraordinary claims is high, it is not impossibly high. If the evidence was good enough, we could be persuaded. The second step of Hume’s argument is his claim that, at least in the case of miracles, the evidence just isn’t good enough. Even though the evidence in favour of miracles might outweigh the evidence against them, in practice this has never happened.

Hume believed that four factors undermine the credibility of reports of miracles. These are: (1) witness credibility – the witnesses to miracles are often unreliable and mistaken; (2) human credulity, which Hume called ‘the love of wonder’ (‘Of Miracles’, p.117) – the curious but widespread human suscep-tibility to the blandishments of strange and marvellous claims; (3) the origins of superstition, often primitive or tribal, cast doubt on their credibility – as Hume put it, these beliefs often come from ‘ignorant and barbarous ancestors’ (‘Of Miracles’, p.119); (4) conflicts of testimony – for any miraculous claim, there is an equally good tradition which denies that miraculous claim. Thus Christianity impugns Islamic miracles, and vice versa.

I repeat that Hume did not claim to have shown that miracles cannot or do not occur. He knew he had done no such thing. Rather, he claimed that it would not be rational, after dispassionately considering the current best evidence, to suppose that they do occur. He was making an empirical argument (that is, based on factual claims) against the credibility of miracles.

Some, though not all of Hume’s points apply to claims about the paranormal. We should, in the spirit of Hume, demand a high (though not impossibly high) standard of evidence before accepting paranormal claims. We should also be aware of and make allowance for the way that the love of wonder can subvert the search for truth.

We should be critically (though not dogmatically) sceptical when confronted with claims that something truly astonishing has occurred. Astonishing claims include such things as telepathy, precognition, clairvoyance, water divining, levitation, astral travelling, channelling, UFO abductions, faith healing, psychic surgery, and a whole raft of claims about ‘New Age’ phenomena – such as claims about healing by pyramids crystals, herbs, or alternative medicine and acupuncture. When confronted with such claims we should follow Hume’s wise example and ask which is more probable; that the alleged effect or event really does or did occur, or that its proponents were somehow deceived or deluded. Or it may be that the anomalous event turns out to be not as extraordinary as it first appeared and that it has a perfectly natural explanation – as is the case, for example, with firewalking.

Hume’s sceptical argument has been stated very schematically. Of course it is necessary to treat each individual claim on its merits. We cannot dismiss claims about, say, alternative medicine or acupuncture a priori. But in the spirit of Hume we should refuse to accept paranormal claims unless powerful and compelling evidence is presented to substantiate them.

Broad, C.D., ‘The Relevance of Psychical Research to Philosophy’ Philosophy 24 (1949), pp.291-309
Hume, David, ‘Of Miracles’, in L.A. Selby-Bigge, ed., An Enquiry Concerning Human Understanding, 2nd edn., pp.108-131, (Clarendon Press, 1902).
Plato, Republic, in Edith Hamilton and Huntington Cairns, eds., The Collected Dialogues of Plato (Princeton University Press, 1961).

© Dr W. Grey 1998

Dr William Grey is a Senior Lecturer in Philosophy at the University of Queensland. He has been a sceptic in all of his previous incarnations.

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