 In Section 1 of this entry, we note certain simple formal relationships between the first six concepts in our initial list above, following the many-centuries old tradition of comparing (and contrasting) basic deontic notions (e.g., obligation, permission) with modal notions (e.g., necessity and possibility). In Section 2, we turn to a benchmark system of symbolic deontic logic, one that quickly became a reference point. In Section 3, we examine a closely related approach that reframes deontic notions by “reducing” them to pure modal notions coupled with a so-called “deontic constant”. In a sense, the approaches discussed in Sections 2 and 3 might be said to stand in the shadow of modal logic. In Section 4, we turn to developments in deontic logic that emerged in the attempt to grapple with conditionalized deontic claims, and here deontic logic comes more fully into its own. In Sections 5 and 6 we turn to a variety of perceived inadequacies of the benchmark systems introduced in Sections 1–4. Section 5 focuses primarily on arguing for and specifying expansions of the limited expressive resources in the benchmark  systems.[5]  Finally, Section 6, rather than expanding on the benchmark approaches, instead raises fundamental shortcomings in their modelling of the ideas they purport to represent, thereby seeking to dismantle some of the principles of the systems and/or construct new systems in their place.