How the diversity of membership of research ethics committees is arrived at has, to date, largely been fairly arbitrary. However, a tool to help determine one's moral preference is now available and it is introduced here as, arguably, having the potential to assist with ensuring a more meaningful diversity amongst an ethics committee's membership. The tool is seen to be easily applied – but, it is argued, may be conceived on at least two false premises. Firstly, despite different theories of (...) ethics, none can be proved to give the ‘right’ answer other than in its own terms. Secondly, if there is an ethical hierarchy, as the model suggests, then ethical diversity must become redundant for the possibility of achieving ethical excellence. (shrink)