README⤓ .txt 2026-07-17T121634.146 000000000000720 Logics of obligation, permission, and prohibition, in which the modal operators carry a normative rather than an alethic reading. The systems formalize what ought to be, what is allowed, and what is forbidden, and confront the paradoxes that arise when norms conflict or are violated.
Action Logic⤓ .md 2026-07-15T073753.000 000000000013728 Segerberg (1980s), Belnap and Perloff (1988). Agency in deontic logic. stit (sees to it that). Actions as logical objects. Foundation for agent responsibility.
Contrary-to-Duty⤓ .md 2026-07-17T120407.600 000000000000792 Chisholm (1963), CTD paradox. Conditional obligations. What to do when violated. Deontic conditionals. Foundation of applied deontic logic.
D Modal Logic⤓ .md 2026-07-15T235628.000 000000000014648 The D axiom (□p → ◇p) as seriality; von Wright's Deontic Logic (1951) is the source of the reading, Hintikka (1957) of the modal treatment, and Kripke's serial-frame semantics (1963) of the system. D = K + D, and Standard Deontic Logic is its normal extension. Serial frames. Ought implies can. Minimal deontic. Foundation of obligation logic.
Deontic Action Logic⤓ .md 2026-07-15T063122.000 000000000018360 Von Wright combined action and deontic logic (1960s). Segerberg, Meyer, and others developed dynamic deontic logic (1980s-90s). Obligations about actions, not just states. "It is obligatory to do α." Foundation for normative multi-agent systems.
Deontic Logic⤓ .md 2026-07-15T052512.000 000000000025488 Georg Henrik von Wright's "Deontic Logic" (1951) founded the modern field. Ernst Mally made earlier attempts (1926) but his system had paradoxes. Extends modal logic to obligation and permission. Developed further by Chisholm, Føllesdal, Hilpinen, and the legal logic community.
Dyadic Deontic Logic⤓ .md 2026-07-15T071525.000 000000000015200 von Wright (1964), Hansson (1969). Conditional obligations: O(A/B). "A is obligatory given B." Handles contrary-to-duty paradoxes. Foundation for normative reasoning.
Formal Ethics⤓ .md 2026-07-16T004643.000 000000000044320 Harry J. Gensler, "A formalized ethical theory" in Symbolic Logic: Classical and Advanced Systems (1990), developed fully in Formal Ethics (1996, Routledge). Builds on Castañeda's insistence that deontic operators attach to imperatives, and on Hare's prescriptivism. Gensler is explicit that it is not a complete ethical theory: the theorems are meant to be the largest common subset of the recognized ethical theories, so that no axiom is controversial.
Imperative Logic⤓ .md 2026-07-15T235811.000 000000000038672 Jørgen Jørgensen, "Imperatives and logic" (Erkenntnis, 1937–38), which posed the dilemma the field is named for; Alf Ross, "Imperatives and logic" (1944), which gave it its standard counterexample; Hare's neustic/phrastic analysis (1949, 1952); Segerberg (1990), Hansen (2008), and Vranas (2008, 2011) for the modern treatments.
Input-Output Logic⤓ .md 2026-07-15T061322.000 000000000019272 Makinson and van der Torre introduced input/output logic (2000). Logic for conditional norms and directives. Not truth-functional: norms don't have truth values. Input: factual situation. Output: what ought to be. Foundation for normative reasoning.
Standard Deontic Logic⤓ .md 2026-07-15T073541.000 000000000013480 von Wright (1951). Obligation and permission. Analogous to alethic modal. KD system. Foundation for normative reasoning.
STIT Logic⤓ .md 2026-07-15T061320.000 000000000020160 Belnap and Perloff developed STIT ("seeing to it that") logic (1988, 1992). Logic of agency and action. Agent "sees to it" that φ: agent's choice guarantees φ. Branching time framework. Foundation for deontic logic of action.
CRITERIA⤓ .txt 2026-07-17T120407.600 000000000000736 Boundary: STIT and action logics belong here when the point is normative agency; pure action-transition modalities without deontic operators belong in Dynamic. Legal and moral argumentation traditions without a formal deontic semantics belong in Argumentation and Rhetoric.