Scholars have long debated the normative rationality, the temporal and legal aspects, and finally the limits and modern practices of parliamentary immunity. Therefore, this study does not insist on these classical interpretations anymore, but seeks to contribute to a comprehensive understanding of the conceptual history of parliamentary immunity. Embracing two schools of thought, the Koselleckian interpretation and the Skinnerian variant, this paper aims to establish and clarify in detail the story of the concept of parliamentary immunity in order to elucidate, in a Socratic fashion, what we really mean when we say that a senator or a deputy benefits from legislative immunity. This inquiry will help us emphasise how this concept leaves behind its abstract notion and becomes an institution with strict rules and practices. In addition, considering the importance of this concept in the modern legislative and rhetoric histories and the frequency with which it is used, this study will question the meanings of parliamentary immunity in the light of different historical settings and will eventually trace out a single, coherent, and unified conceptual matrix. My contention is that once parliamentary immunity – seen as a conceptual construct only adjusting the balance of power between the executive and the legislative powers – becomes an institution with strong practices, it enforces the parliament as a unified and independent body and creates the prerequisite conditions for the democratic development.