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Risk-Benefit Analysis: From a Logical Point of View

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Abstract

In this paper I am concerned with risk–benefit analysis; that is, the comparison of the risks of a situation to its related benefits. We all face such situations in our daily lives and they are very common in medicine too, where risk–benefit analysis has become an important tool for rational decision-making. This paper explores risk–benefit analysis from a logical point of view. In particular, it seeks a better understanding of the common view that decisions should be made by weighing risks against benefits and that an option should be chosen if its benefits outweigh its risks. I devote a good deal of this paper scrutinizing this popular view. Specifically, I demonstrate that this mode of reasoning is logically faulty if “risk” and “benefit” are taken in their absolute sense. But I also show that arguing in favour of an action because its benefits outweigh its risks can be valid if we refer to incremental risks and benefits.

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Notes

  1. Be it noted that, strictly speaking, only quantitative risk-benefit analysis allows calculating a so-called risk:benefit ratio. For example, Roberts (1985) discusses in a quantitative study the problem of food-borne diseases and their prevention by irradiation. He holds that “both irradiation of chicken and pork appear to have a favourable benefit/cost ratio of 2 or more” (1985, 963). However, some authors use the term “risk:benefit ratio” also in their qualitative analyses (e.g., Allen and Luger 2002; Zuppa and de Luca 2003). But this use is not helpful since it can only be metaphorical.

  2. See also Bogousslavsky (1996), Pochin (1982), and Wu (2004). Sieber and Adamson, moreover, hold regarding maintenance therapy in myeloma: “Even if multiple myeloma patients treated with melphalan are at a higher risk of developing acute leukaemia than is the general population [an incremental risk], the consensus among clinicians appears to be that the increases in survival time and in the quality of life of melphalan-treated patients far outweigh the risk of drug-induced acute leukaemia” (1975, 557).

  3. Compare also Buchanan and Miller (2006) and Orme (1990), who argues for the use of thiazides in treating hypertension because the benefits outweigh its risks. Among the risks is the fact that thiazide diuretics cause hypokalaemia (an absolute risk) and may increase the serum cholesterol concentration (an incremental risk).

  4. Attitudes toward risk differ. Some people are risk-seeking, but research suggests that most of us are somewhat risk-averse. If a person is neither risk-seeking nor risk-averse, he or she is said to be risk-neutral.

  5. There is a fundamental disagreement in the philosophical literature over the conclusion of practical reasoning. Some hold that it is an action, while others reject this as inadequate and contend that it must be an intention, a decision, or an imperative. Throughout this essay, I shall assume that the conclusion of a piece of practical reasoning is an intentional attitude (e.g., your wanting that x is performed or your preferring x to y). In ordinary speech, such conclusions can be expressed in different ways—e.g., by holding that one should do something or that it would be better to do it. That is to say, the conclusion “women should receive tamoxifen treatment” is the expression of the reasoner’s preference for this therapy.

  6. Some authors take “risk” as synonymous with “probability.” Strictly speaking, however, the probability of a bad outcome is in risk–benefit analysis only one component of the risk associated with an option. To the different meanings of “risk” and “benefit,” compare Hansson (2005), Iltis (2005), and Pochin (1982).

  7. The example has been adapted from Hammond, Keeney, and Raiffa (1999, 131–133). I have used a slightly different version of this example in another paper, albeit in a different context.

  8. It should be noticed that, in medicine, we are often facing problems so vague that we cannot assign probabilities. In such cases, we need to rely on nonprobabilistic risk–benefit analysis, which is based solely on the value of the outcomes and ignores their probabilities. In nonprobabilistic risk–benefit analysis, we have only possibilities available. Holding that an event is possible is making an extremely weak claim. We are only saying that it is not impossible that the event occurs, which, in turn, is to say that it is not necessary that it does not occur. Nonprobabilistic problems occur frequently in medicine. For example, the World Medical Association holds that “if the risk is entirely unknown, then the researcher should not proceed with the [research] project” (2009, 104–105); and in the 1970s, the U.S. Food and Drug Administration denied approval of Depo-Provera for use as a contraceptive partly because it was unclear how likely a higher incidence of breast cancer, found in beagle dogs, was applicable to humans (Guttmacher Institute 1978). Since there is no space here to go into the details of nonprobabilistic risk–benefit analysis, I can only mention that the “benefit-outweighs-risk” mode of reasoning can be shown to be valid in nonprobabilistic reasoning, too, if we reconstruct the reasoning by ignoring probabilities (which results in an analysis akin to the application of Laplace’s maxim of equal probability).

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  1. Department of Philosophy and Applied Ethics, The University of Zambia, P.O. Box 32379, Lusaka, Zambia

    Georg Spielthenner

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Spielthenner, G. Risk-Benefit Analysis: From a Logical Point of View. Bioethical Inquiry 9, 161–170 (2012). https://doi.org/10.1007/s11673-012-9366-y

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