The principle of proportionality revisited: interpretations and applications

The principle of proportionality is used in many different contexts. Some of these uses and contexts are first briefly indicated. This paper focusses on the use of this principle as a moral principle. I argue that under certain conditions the principle of proportionality is helpful as a guide in decision-making. But it needs to be clarified and to be used with some flexibility as a context-dependent principle. Several interpretations of the principle are distinguished, using three conditions as a starting point: importance of objective, relevance of means, and most favourable option. The principle is then tested against an example, which suggests that a fourth condition, focusing on non-excessiveness, needs to be added. I will distinguish between three main interpretations of the principle, some primarily with uses in research ethics, others with uses in other areas of bioethics, for instance in comparisons of therapeutic means and ends. The relations between the principle of proportionality and the precautionary principle are explored in the following section. It is concluded that the principles are different and may even clash. In the next section the principle of proportionality is applied to some medical examples drawn from research ethics and bioethics. In concluding, the status of the principle of proportionality as a moral principle is discussed. What has been achieved so far and what remains to be done is finally summarized.