A moral theory holding that moral norms are those principles that no one could reasonably reject when justification must be given to others affected by those principles; justification to persons—not aggregate welfare or historical contracts—is the central standard.

Principle

A norm is morally binding if it can be justified to each person on grounds they could reasonably accept; moral legitimacy depends on interpersonal justifiability rather than on actual consent or maximization of aggregate good.

Demonstration

Illustrative scenario → A local policy proposes permitting a factory to emit pollutants that harm nearby residents while benefiting distant consumers. Under contractualist reasoning, the policy is evaluated by whether the harms and benefits can be justified to affected residents; if the residents have reasonable grounds to reject the policy because the harms they bear are not justifiably outweighed, the policy fails the contractualist test.

Misapplication

Conflating contractualism with actual contractual consent or with majority voting: the semantic error is treating it as requiring express agreement or numerical endorsement. Contractualism concerns hypothetical or reasoned justifiability to each person, not historical signatures or tallied votes.

Consequence

Correct application reframes moral debate around what others can reasonably accept, emphasizing respect for persons and reasons rather than aggregate trade‑offs; it yields moral constraints that protect individuals from policies they could reasonably reject.

Reversal

When there is reasonable disagreement about what counts as a reasonable rejection or when parties lack capacity to participate in justificatory exchange (e.g., children, severely cognitively impaired), contractualist standards must be adjusted (e.g., by using representative or proxy justifications), which qualifies straightforward application.

Boundary

Clearly within: theories that center morality on justifiability to persons (e.g., Scanlonian‑style contractualism). Boundary case: social contract theory—concerned with political legitimacy and institutional design via agreements among members of a polity, which overlaps but addresses different questions. Clearly outside: aggregative consequentialist accounts that ignore individual justifiability.

Semantic Tension

Tension with Consequentialism over whether justification is interpersonal acceptability or aggregate good; tension with Social Contract Theory over moral versus political focus and the role of explicit versus hypothetical agreement.

Synthesis

Contractualism relocates moral authority to the domain of interpersonal justification: its core insight is that moral norms gain force insofar as they survive scrutiny from those they govern, producing a justificatory standard distinct from consent or utility maximization.