What is "contractualism"

n. (context politics English) A political theory based on the idea of a social contract between a ruler and their subjects.

Contractualism is a political position that holds that if an individual breaks the contract then the other person(s) involved no longer need to respect the condition of the contract.

For instance: Bob has an abstract contract with Billy stating that if Billy lets Bob use his toys then Bob will let Billy play with his toys. Contractualism states that if Billy stops letting Bob use his toys, since the abstract contract is broken, Bob no longer has to let Billy use his toys.