Coherence and Morality

Coherence and Morality Carl G. Hempel The Journal of Philosophy, Vol. 62, No. 19, American Philosophical Association Eastern Division Sixty-Second Annual Meeting. (Oct. 7, 1965), pp. 539-542. Stable URL: http://links.jstor.org/sici?sici=0022-362X%2819651007%2962%3A19%3C539%3ACAM%3E2.0.CO%3B2-K The Journal of Philosophy is currently published by Journal of Philosophy, Inc..

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SYMPOSIUM: ETHICS AND DECISION THEORY

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with the best will in the world, agent 1 will not be able to find a proposition E that will serve the purpose when A is the proposition that agent 1 will die immediately and B is the corresponding proposition about agent 2. But, if the mirroring trick is applicable to a sufficiently extensive and varied coherent subranking of agent 2's preferences, the two rankings may plausibly be correlated by setting desl (AE) = des2A for each proposition A in the subranking. The desirabilities of the rest of the propositions in the two full rankings will then be determined by their relationships to propositions in the subrankings. (In Ramsey's theory or in the present theory, once the desirabilities of two or of three differently ranked propositions are fixed, the desirabilities of all other propositions in the ranking are determined.) Alternatively, by applying the sorts of consideration that arise naturally in discussions of fairness, one might alter the mirroring so as to extend the domain of comparability by such devices as permuting appropriate proper names, so that with A and B as in the preceding paragraph we have desl (AE) = des2 B and desl (BE) = dess A for some (now, more plausible) proposition E. THECITYCOLLEGE CITYUNIVERSITY OF NEWYORK

RICHARD C. JEFFREY

COHERENCE AND MORALITY ' of moral deliberation in the light of current logical ANandanalysis mathematical theories of decision is, I think, an important undertaking, and Professor Jeffrey's paper provides illuminating illustrations of the kinds of insight this approach may yield and of the problems it raises. Jeffrey's decision-theoretical model is applicable especially to situations where an agent wishes to make a choice among several courses of action that he believes to be available to him, each with a set of "possible outcomes.'' To each of the outcomes, the agent is assumed to assign, in accordance with his beliefs and preferences, (i) a probability of its occurrence as a result of the relevant action, and (ii) a valuation expressed by a numerical desirability. The decision rule Jeffrey proposes for these cases is based on Bayes' principle, which assigns to each action a desirability that is defined as the probabilistically weighted average of Abstract of a paper to be delivered in an APA symposium, commenting on Richard C. Jeffrey, "Ethics and the Logic of Decision," this J O ~ A 6 L69,, 19

(Oct.

7, 1965) : 528-539.

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the utilities of its different possible outcomes. An optimal d+ cision will then select an action for which this desirability is maximal. Although the basic conception of the model is Bayesian, the specific form Jeffrey gives it includes some interesting technical innovations. Thus, for example, he represents actions by propositions (to the effect that such and such action is taken), and he assigns desirabilities not only to propositions that characterize actions, but to all propositions expressible in that fragment of the agent's language in which he formulates his deliberations. These desirabilities are fully determined by the "expectation principle" once desirabilities and probabilities have been assigned to the "basic cases," i.e., to the relatively most specific propositions expressible in the given language fragment. There follows the interesting result that, even though the desirabilities of the basic cases may be chosen independently of their probabilities, nevertheless a change in the probabilities alone, reflecting a change in belief, may entail a change in the desirabilities of some nonbasic propositions, such as those indicating the possible outcomes of a contemplated action. Jeffrey's model offers us just one general rule of deliberation, namely, to choose a preference ranking that is coherent in the sense of being derivable from basic probability and desirability assignments in conformity with the expectation principle. This leads to his question whether coherence by itself affords "a sufficient basis for all morality." He does not make clear, however, just what features he would take to qualify a rule as such a " s d c i e n t basis." His discussion suggests that he is concerned with something I will vaguely refer to as the "moral soundness" of the resulting decisions, and perhaps also with the avoidance of disruptive conflicts between the preferences of different agents using the rule. Surely neither of these desiderata is guaranteed by the formal rule of deliberation alone; and indeed, Jeffrey notes that a radical optimism concerning human nature is required if coherence is to be adopted as a s d c i e n t basis for moral deliberation. But, since the qualifying characteristic for such a basis is not made explicit, it remains unclear what specific assumptions about human nature such optimism would imply. Moreover, it seems that, in addition to some form of "moral optimism" concerning human nature, the use of coherence as the basic standard of moral deliberation would also require a "cognitive optimism" concerning the agents' ways of forming their empirical beliefs. For grave conflicts could arise over a given

XYMPOSIUM: ETHICS AND DECISION THEORY

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moral issue even among agents who assign the same desirabilities to all basic cases, if they differ strongly in their probability assignments. I n his smoking example, Jeffrey mentions statistical evidence as a possible guide for the choice of subjective probabilities: but what if some agents assigned their probabilities in a counterstatistical way ? Incidentally, some experimental studies suggest that the subjective probabilities representing the expectations of even quite intelligent agents may be distinctly at variance with relevant statistical inforlnation available to them. Thus, I wonder whether some additional requirement of rationality must not be imposed upon the choice of probabilities and, if so, what form it might take. Jeffrey offers his model as a "framework within which any correct deliberation can be presented." Some moral decisions are usually viewed as being dictated by just one more or less specific qualitative standard, such as the golden rule, or the principle that killing-with specified exceptions-is evil. Can the model accommodate such cases? A moral principle of the kind here considered would have to be construed as assigning a strong negative desirability to the disjunction of those basic cases which involve a violation of the principle. But this will normally be quite insufficient to assign definite desirabilities to all the propositions relevant to the deliberation, and the decision supposedly reached by means of the principle cannot, therefore, be obtained within the Jeffrey model. But, rather than pointing out a weakness of the model, this consideration should be taken to show, I think, that the construal of a moral decision as determined by one principle of the kind here referred to involves a considerable oversimplification; for an action is always performed in some particular setting many of whose features may be relevant to its moral evaluation. Finally, two basic questions-one of them theoretical, the other moral-concerning the justifiability of choosing the Bayesian maxim as a basic rule of moral deliberation. Even within the mathematical theory of decision, the Bayesian approach is rejected by a group of theoreticians who qucstion the possibility of assigning probabilities to propositions except in those special cases where the probabilities can be interpreted in terms of statistical frequencies. 'In other cases, decisions have to be made "under uncertainty," i.e., without the benefit of probabilities; and, interestingly, the pattern those theoreticians propose for such decisions is basically the same as that of the argument which Jeffrey cites and rejects as an example of "fallacious" deliberation.

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Secondly, adherence to the Bayesian rule might be questioned also on the moral ground that it makes the decision in a moral conflict strongly dependent upon the probabilities of success of the alternative actions under consideration. The rule may, therefore, direct us to refrain from an action that could bring about a very high good and to act instead in an alternative way, whicheven at best-will yield a much lesser good, but which has a greater probability of success. CARL G. HEMPEL PRINCETON UNIVERSITY

COMMENTS ON RICHARD C. JEFFREY'S "ETHICS AND THE LOGIC OF DECISION" * I n this interesting paper, Professor Jeffrey suggests the thesis that some of the formal models developed in statistical decision theory provide a useful and constructive device for understanding certain theoretical problems in ethics. Two such problems, considered as examples, are: (1) the normative character of coherent preference rankings, and (2) the interpersonal comparison of utilities. Parts of the development of his position are contained in his forthcoming book, The Logic of Decision; presumably, the questions raised here are answered there. I n any case, the following is intended to bring up issues essential to the evaluation of the thesis rather than to make any closed judgment. Indeed, it is clear that Jeffrey's paper should be understood as a proposal.

To the naive reader, many of the concepts developed formally seem to suffer from the absence of appropriate experimental identification. For example, in the discussion regarding value and belief, it is asserted that "we must think of propositions as disjunctions of basic cases (themselves propositions). " However, it isn't stated how one determines whether or not a given proposition is a basic case. If the rule is, as would suit the requirements of the formal model, that A is a basic case if and only if des A is constant for the agent (over all other cases?, over time?, etc.), then an element of circularity appears. If, however, the rule is a more fundamental one from which such constancy may be deduced, it would be extremely useful to have it stated. Some rule seems Abstract of a paper to be presented in an APA symposium, commenting on Richard C. Jeffrey, "Ethics and the Logic of Decision," this JOURNAL,62, 19 (Oct. 7, 1965) : 528-539.