​This paper discusses Prognosis Theory, arguing that legal science as a social science today cannot escape the normative issues of justice and ethics in the practice of justice. These problems cannot simply be rejected as unscientific. The paper begins with an overview of the Prognosis Theory of law, before moving to a discussion of Alf Ross's Prognosis theory as formulated in On Law and justice. It then presents some of the objections to Prognosis Theory. The paper concludes that the description of the applicable law is not sufficient, but that it must be supplemented by normative considerations on the applicability of the legal sources and basis for the legal method.