30 Chapter 2 Strikingly, in this debate, proponents and opponents of PS use the same ethical principles (autonomy, beneficence, nonmaleficence) but interpret them in totally different ways. Ethical discussions are often held on the level of these ethical principles only, with moral intuitions moving between extremes; for example, PS as a blessing versus treatment as an evident danger or a definite competence of the child versus incompetence because the child is simply too young and has an immature developmental level to decide on these substantial issues. What is missing in the discussions is an exploration of underlying ideas and theories about the nature of gender (dichotome or fluid) and GD (mental illness or social construct), child welfare, and child competence. Proponents and opponents seem to have different views on these issues, often without openly stating them. It is an essential task to elucidate these underlying ideas and theories because they substantially influence the judgment on GD treatment. Strikingly, in the literature on GD, most of the times, only proponents give arguments for their treatment position. It is difficult to find arguments against the use of PS as a treatment option as opponents rarely publish in professional journals. Therefore, to date there is no clear overview of the considerations of proponents and opponents regarding the use of early medical interventions for GD. An overview explicating considerations, which underlie the different views on PS, could be the first step towards a more consistent approach recommended by clinicians across different countries. The aim of our study was to explicate the considerations of proponents and opponents of PS to move forward the ethical debate. For this purpose, we have performed an empirical ethical study to answer the following questions: (1) what are the moral intuitions (direct thoughts or opinions) of informants on puberty suppression in GD; (2) what are the (underlying) ideas, assumptions, and theories of informants about the aetiology of GD, and the concepts ‘gender’, ‘child competence’, and ‘best interests’?; and (3) do moral intuitions, ideas, and theories of proponents of PS differ from those of opponents, and in what sense? METHODS An empirical ethical approach was followed, using a qualitative interview and questionnaire study. The study was approved by the institutional review board of the Leiden University Medical Centre. Fifteen professionals participating in the study were interviewed face-to-face, six by using Skype (Microsoft Corp., Redmond, WA). Some treatment teams indicated that they did not master the English language well enough for a direct interview. These teams were