Conventionalism is the philosophical attitude that fundamental principles of a certain kind are grounded on (explicit or implicit) agreements in society, rather than on external reality. Although this attitude is commonly held with respect to the rules of grammar, its application to the propositions of ethics, law, science, mathematics, and logic is more controversial.
The French philosopher Pierre Duhem espoused a broader conventionalist view encompassing all of science. Duhem was skeptical that human perceptions are sufficient to understand the "true," metaphysical nature of reality and argued that scientific laws should be valued mainly for their predictive power and correspondence with observations.
According to conventionalism as defined by Dworkin, a community's legal institutions should contain clear social conventions relied upon which rules are promulgated. Such rules will serve as the sole source of information for all the community members because they demarcate clearly all the circumstances in which state coercion will and will not be exercised.
Dworkin nonetheless has argued that this justification fails to fit with facts as there are many occasions wherein clear applicable legal rules are absent. It follows that, as he maintained, conventionalism can provide no valid ground for state coercion. Dworkin himself favored law as integrity as the best justification of state coercion.
One famous criticism of Dworkin's idea comes from Stanley Fish who opines that Dwokin, like the Critical Legal Studies movement, Marxists and adherents of feminist jurisprudence, was guilty of a false 'Theory Hope'. Fish claims that such mistake stems from their mistaken belief that there exists a general or higher 'theory' that explains or constrains all fields of activity like state coercion.
Another criticism is based on Dworkin's assertion that positivists' claims amount to conventionalism. H. L. A. Hart, as a soft positivist, denies such claim as he had pointed out that citizens cannot always discover the law as plain matter of fact. It is however unclear as to whether Joseph Raz, an avowed hard positivist, can be classified as conventionalist as Raz has claimed that law is composed "exclusively" of social facts which could be complex, and thus difficult to be discovered.
In particular, Dworkin has characterized law as having the main function of restraining state's coercion. Nigel Simmonds has rejected Dworkin's disapproval of conventionalism, claiming that his characterization of law is too narrow.