Public Morality is the morality that most of society agrees upon.  For instance we all agree that rape, murder and theft are all immoral.  There doesn't seem to be a need for much discussion and those that think differently may be perceived as a threat either to the individual or to society at large.  How the public morality is developed may depend upon the philosopher.  Lord Patrick Devlin connect morality to religion and it is through the acceptance of religious belief that morality is transmitted.  Lon Fuller has a much more complex concept of public morality, but still insists that morality as the basis for law.  Ronald Dworkin has a more deductive method of determining morality and asserts that this morality is public rather than private in nature when it is applied to the law. 

A problem associated with public morality is the relationship of public morality to private morality.  Devlin denies the possibility of private morality and claims that the true morality can only be public morality.  Morality that cannot be shared and agreed upon is of no value to Devlin.

Dworkin is unclear about a distinction between public and private morality.  Dworkin has a method for convincing others about morality that depends on logic and evidence.  However, because Dworkin cannot separate legality from morality, Dworkin's morality functions as a public morality giving his legality validity.