• README ⤓ .txt 2026-10-22T165042.936 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 2026-08-20T024705.000 000000000033416
  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 2026-10-22T165042.936 000000000000792
  Chisholm (1963) gave four sentences about a duty and its violation which are jointly consistent and logically independent as English, and showed that Standard Deontic Logic has no formalization of them possessing both properties. The paradox set the agenda for conditional obligation: dyadic operators (Hansson 1969, Lewis 1973), temporal treatments (Thomason 1981, van Eck 1982), defeasible ones (Prakken and Sergot 1996), and Åqvist's systems E, F and G are all answers to it.
• D Modal Logic ⤓ .md 2026-10-22T090057.000 000000000034504
  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. Consistency of obligation. Minimal deontic. Foundation of obligation logic.
• Deontic Action Logic ⤓ .md 2026-08-20T025146.000 000000000034488
  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 2026-08-20T032646.000 000000000041656
  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 2026-10-22T090936.000 000000000034368
  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 2026-08-20T031153.000 000000000050968
  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 2026-10-22T092906.000 000000000042224
  Jørgen Jørgensen, "Imperatives and logic" (Erkenntnis, 1937–38), which posed the dilemma the field is named for; Alf Ross, "Imperatives and logic" (Theoria, 1941; reprinted 1944), which gave it its standard counterexample; Hare's neustic/phrastic analysis (1952); Segerberg (1990), Hansen (2008), and Vranas (2008, 2011) for the modern treatments.
• Input-Output Logic ⤓ .md 2026-10-22T085413.000 000000000042856
  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.
• Preference Logic ⤓ .md 2026-10-22T180154.561 000000000000792
  Sören Halldén, On the Logic of "Better" (Library of Theoria 2, Lund: Gleerup, 1957), gave the first complete calculus of the comparative value concepts "better" and "equal in value", and Georg Henrik von Wright, The Logic of Preference (Edinburgh University Press, 1963), grown from his Edinburgh lectures, fixed the field's name, its prohairetic calculus, and its disputes. The modal reconstruction over a betterness ordering is due to Johan van Benthem, Patrick Girard and Olivier Roy, "Everything Else Being Equal: A Modal Logic for Ceteris Paribus Preferences" (Journal of Philosophical Logic 38(1): 83–125, 2009); the dynamics began with van Benthem and Fenrong Liu, "Dynamic logic of preference upgrade" (Journal of Applied Non-Classical Logics 17(2): 157–182, 2007), and Liu's Reasoning about Preference Dynamics (Synthese Library 354, Springer, 2011) is the systematic treatment.
• Standard Deontic Logic ⤓ .md 2026-08-20T023201.000 000000000034568
  von Wright (1951). Obligation and permission. Analogous to alethic modal. KD system. Foundation for normative reasoning.
• STIT Logic ⤓ .md 2026-08-20T030748.000 000000000039952
  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 2026-07-15T161332.000 000000000007424
  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.