Legal professionals need to identify the law to be able to answer legal questions. It is therefore necessary to know how this can be done: which sources should be used to construct the law? Answers have widely varied throughout time, but legal doctrine (i.e. the practice of normatively stating the law’s content) has remained largely ignored. Since empirical research has demonstrated that legal doctrine does influence the behavior of legal actors, this project wants to help developing an adequate sociology of legal doctrine. Against the background of the theory of legal formants, legal evolutionism, and argumentative approaches to law, this project will scrutinize the normative positions and arguments expressed by legal scholars between 1948 and 2023 in stating the content of the Belgian law of obligations relating to two specific cases of punitive elements: excessive penalty clauses and refusal of restitution. Both cases illustrate a deeper tension between the public value of deterrence of unlawful conduct and the private value of avoiding unjustified enrichment. This tension allows for a variety of normative positions, making them ideal cases. Said normative positions and arguments will be investigated by combining a qualitative content analysis with a quantitative citation network analysis. This will enable to shed new light on i.a. the so-called ‘prevailing opinion’ and to test legal evolutionism as a prism to look at the sources of law.