A fallacious jar? The peculiar relation between descriptive premises and normative conclusions in neuroethics.

Ethical questions have traditionally been approached through conceptual analysis. Inspired by the rapid advance of modern brain imaging techniques, however, some ethical questions appear in a new light. For example, hotly debated trolley dilemmas have recently been studied by psychologists and neuroscientists alike, arguing that their findings can support or debunk moral intuitions that underlie those dilemmas. Resulting from the wedding of philosophy and neuroscience, neuroethics has emerged as a novel interdisciplinary field that aims at drawing conclusive relationships between neuroscientific observations and normative ethics. A major goal of neuroethics is to derive normative ethical conclusions from the investigation of neural and psychological mechanisms underlying ethical theories, as well as moral judgments and intuitions. The focus of this article is to shed light on the structure and functioning of neuroethical arguments of this sort, and to reveal particular methodological challenges that lie concealed therein. We discuss the methodological problem of how one can--or, as the case may be, cannot--validly infer normative conclusions from neuroscientific observations. Moreover, we raise the issue of how preexisting normative ethical convictions threaten to invalidate the interpretation of neuroscientific data, and thus arrive at question-begging conclusions. Nonetheless, this is not to deny that current neuroethics rightly presumes that moral considerations about actual human lives demand empirically substantiated answers. Therefore, in conclusion, we offer some preliminary reflections on how the discussed methodological challenges can be met.