This article is concerned with the role empirical research can play in normative practical ethics. There is no doubt that ethical research requires some kind of collaboration between normative disciplines and empirical sciences. But many researchers hold that empirical science is only assigned a subordinate role, due to the doctrine that normative conclusions cannot be justified by descriptive premises. Scientists working in the field of ethics commonly hold, however, that the empirical sciences should play a much bigger role in ethical (...) research. The aim of this paper is to show that empirical sciences can play a substantive role in normative ethics, with no illicit inferences from is to ought. To achieve this aim, I explain Hume’s thesis. In the following sections, I am concerned with different uses of empirical data that do not imply an illicit inference from descriptive premises to a normative conclusion. The article demonstrates that there are many modes of ethical reasoning that allow for a substantive use of empirical data, and it also shows the importance of Hume’s thesis for clarifying ethical reasoning. (shrink)