To appear in Heams et al. (eds.), Handbook of Evolutionary Biology (provis. Title), Springer.

Please do not quote without permission. This is not the final version

subjects’ brains were scanned with the aid of a brain imaging technique. The results of the experiment show that emotional involvement has a great influence on moral judgements: imagining having to push a person under a trolley going at full speed in order to stop it (and thus, saving the five hikers) is more emotionally salient (this is translated as increased brain activity in the areas correlated to emotions) than imagining pushing a lever that will direct the trolley onto a track where there is a person. This difference in emotional engagement leads subjects to refuse the first action and to judge the second to be morally permissible, even though the life of one person is weighed against the lives of five people in both cases. Thus, the subjects’ choice in the footbridge case seems to depend mainly on a physiological reaction that is linked to the proximity or physical contact with a person. The reason I have taken the time to explain the details of these experiments is twofold. On the one hand, the collection of results from these three empirical tests puts pressure on the idea that common sense can easily provide us with intuitions of a moral type that will be trustworthy, coherent, and on which it is possible to found an ultimate moral theory. In fact, to interpret the moral judgements produced in the framework of the three aforementioned contact32 experiments, one cannot escape the explanation of physical .With these empirical data in mind, it is difficult to suppose that there exists a widely-shared moral sense that is ultimately capable of justifying our values and moral choices. On the other hand, these results favour a descriptive analysis of the moral phenomenon, an analysis of the kind in which evolutionary considerations can play a role. Without wanting to give too much credit to post-hoc explanations, we can note that an evolutionary theorist would hardly be surprised by the existence of this law of physical proximity (see Appiah 2008). At the time when our social instincts were slowly forged, human beings probably lived in small communities in which it was important to help exactly the members of their group, in other words the people in danger who were ‘right beside them’. These systems allowed our ancestors to respond rapidly in everyday situations of danger. Following this logic, it is understandable that we have less difficulty accepting the distress of people physically distanced from us, or the lack of aversion in the loop case.

What can we conclude from this discussion? Looking for irrefutable foundations for our moral norms seems to be a lost cause because the most primary moral intuitions are often not morally rationalisable. However, if we lower our expectations in terms of grounding moral norms, and if we accept that we should be content with producing the best possible reasons for accepting one norm over another, factual data (including of an evolutionary kind) will clearly play a large part in the enterprise of moral justification. There are many ways of using empirical material to justify our moral convictions. For example, a modest attempt would be to make use of criteria such as feasibility, coherence, functionality, or compatibility with our emotional responses and those of our peers. None of these criteria could be considered ultimate, but together they could allow us to legitimate our moral convictions (along these lines, see Gibbard 1990). Deep reflection on this question will lead us too far from the topic at hand, but it should be acknowledged that evolutionary considerations (notably those relating to the functionality of a behaviour) can prove relevant within the framework of this kind of normative enterprise.

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