… [ snip ]
- Although it is Parfit’s views about motivation, reasons, and ethics that concern me, I am going to start with a comparison at a little distance from his discussion, and indeed from moral philosophy altogether, in the theory of probability. We return to moral philosophy soon enough.
- Single case probabilities are those of particular events, such as Eclipse winning the 2.30pm race this afternoon, or my dying within the next twelve months. The contrast is with probabilities whose topic is general, and more naturally introduced with the indefinite article: ‘the probability of a child being autistic’ or ‘the probability of a philosophy book weighing over two kilos’, for example. Here frequencies provide natural truth-conditions, or truth-makers, but in the single case it is not so easy, and this motivates the pessimistic but plausible view that no satisfactory theory of such probabilities is to be had. Frequencies require sets of events, and putting singular events into sets does not help unless we have a principle for selecting the right sets. Any such principle is in danger of leaving all single case probabilities at either 0 or 1, although we will usually not know which, or, if the world is indeterministic, leaving them equally unknowable. Hence, probabilists such as Richard von Mises had banned them altogether, and scepticism about the notion — either counseling elimination, or at best an error theory — seemed to be the only scientific course.
- And yet outside the philosophy classroom the notion refused to die. Horse races still took place, and bookmakers thrived as before. Discussions about a particular horse’s chances filled sporting columns and bars. Insurance companies and actuaries still worked. People made up their minds, or changed them, oblivious to the pained cries of philosophers. So Ramsey, more charitable than von Mises, offered an explanation and vindication of the practices connected with voicing and discussing single-case probabilities. The manifestation, he said, of a sincere judgment of this kind is a distribution of confidence, and that in turn can most easily be regarded as a disposition to buy or sell bets at appropriate prices, under certain idealized conditions. Such dispositions, of course, are not true or false in themselves. But they have what I called a propositional reflection, in the single case judgment. Thus, if I am inclined to risk $1 on Eclipse winning the 2.30, in the hope of getting $2 back if he does, I can voice this disposition by saying that Eclipse’s chances are at least 50 – 50. The disposition is discussable, for it may be that this is a very foolish bet. If you know that Eclipse is off-form, or entirely outclassed by the field, or has shown symptoms of equine flu, you may helpfully seek to dissuade me. It is these discussions that fill racecourse bars and the sporting columns and the single-case probability proposition is the focus for them. This is only a sketch of Ramsey’s story, but it represented, in my view, a considerable improvement on the error theory of von Mises, or indeed any other proposal on the table. It is naturalistic, explanatory, and justificatory, all in one shot.
- Consider now a bookmaker Bill who is worth listening to on his subject. He offers odds more shrewdly than his competitors — that is, while offering better prices than they do, thereby attracting punters, he still makes a nice profit. Bill listens to gossip, looks at gallops, studies form more carefully than, say, a worse bookmaker, Kevin. Bill can offer 100 to 1 against horses like Eclipse, say, and still rake in a profit, although Kevin only dares offer 10 to 1 against it: a worse price, with fewer buyers, netting less profit.
- Nevertheless, Bill will not regard himself as infallible. There may be occasions when he kicks himself, not because an outsider won, since the improbable sometimes happens, but because he should have known better. He neglected a possible source of evidence, relied on a stable boy of whose plausibility he should have been more wary, and so on. ‘I was wrong’, he might say, ‘Eclipse’s chances were nothing like as bad as I made out’. In other words, Bill has, in thought or talk, a discursive practice of improving and refining his sensitivity to evidence, and thence his dispositions to buy and sell bets, and to make the judgments that are the propositional reflection of those dispositions. Kevin does the same, but is not as good at it as Bill.
- In all such thought and discourse, the single-case probability is quite naturally, and quite faultlessly, treated as a topic. But now the single-minded, or indeed myopic, philosopher comes along, and says that this is all very well, but what on Ramsey’s theory does the truth that Eclipse’s chances have one value or another consist in? This is not a particularly useful question, for as I discuss below, it is shoehorning a distinctively pragmatic theory about the nature of a practice, into one working in terms of truth-conditions. If it is insisted upon, it can get either of two answers. One is the unhelpful homophonic answer: it is true that Eclipse’s chances are high if and only if Eclipse’s chances are high. Alternatively, the response might be to point to the evidence — the standards in virtue of which Eclipse is to be regarded as a good bet, or the grounds for his being a good bet: such things as him being fit, trained, healthy, ridden by a champion jockey and having a better record than the rest of the field. These are not the things that identify the semantics of the term — ‘being ridden by a champion jockey’ is no part of the meaning of ‘likely to win’. The semantic anchor of the judgment lies in the dispositions that make up the degree of confidence in the event. But these grounds are the kinds of things to which Bill is exquisitely sensitive. Kevin is not.
- We now turn to ethics, where, over many years, I have tried to articulate and defend a parallel position, standing, for instance, to error theorists exactly as Ramsey stood to von Mises. Moral and evaluative propositions are foci for the arguments and thoughts with which men and women discuss, reject, accept, ways of conducting their lives. We urge them on each other in order to change peoples’ practical inclinations: their motivations and concerns, their sense of honour, guilt and shame, or of what will do and what will not. So now I turn to examples of the things Parfit says, and see how they might sound if we applied them to Ramsey’s theory. Since I do not want to put words into Ramsey’s mouth, I shall invent a persona, Bramsey, to act as his spokesman.
- See Web Link for what may be a draft, I've not checked it thoroughly.
- The "Author's Introduction" given in the Abstract is taken from this source.
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