As John Merryman explains in his famous handbook on the civil law tradition, in continental Europe the standard attitude is that the law is certain and should appear so, and that this certainty would be impaired by noting dissents and by publishing separate opinions. It seems that the common law tradition, where judges write separately on a rather regular basis, is less obsessed with legal certainty, and considers other values, such as justice, transparency and legitimacy as equally, if not more, important. The paper aims at examining the paradoxical and counter-intuitive relationship between legal certainty and the possibility of publishing separate opinions. There is a paradox, because even if an apparently unanimous decision seems to enhance legal certainty, as the court speaks with one voice and gives only one answer to each legal question at hand, at the same time it endangers the predictability of the law, as future changes in case-law are more difficult to foresee. Thus, non-unanimous judgments demonstrate that there is a contrast between the two basic elements of legal certainty: consistency and predictability. This account of the relationship between legal certainty and dissenting opinions, however, reveals a positivist approach which sees the law as a set of rules. A non-positivist understanding of legal certainty, regarding deliberative reasoning as a defining element of law, focuses on the certainty of argumentative practices as something distinctively different from the certainty of normative elements. In this argumentation-based perspective, elaborated by Stefano Bertea, the object of legal certainty is an argumentative activity and so procedural law. In Habermas’s view procedural certainty consists in non-arbitrariness, i.e. that in procedures issuing judicial decisions only relevant reasons are decisive. Legal certainty, thus, incorporates a procedural and a rational component. The paper will attempt to shed new light on the different paradigms of legal certainty by discussing the phenomenon of judicial dissent from a theoretical and comparative perspective.