Sentence:  Walzer speculates that a comparison of the moral codes found in various societies might produce "a set of standards to which all societies can be held—negative injunctions, most likely, rules against murder, deceit, torture, oppression, and tyranny." These standards would constitute "the <WSD>moral minimum</WSD>." 
Meaning of the word marked with <WSD> tags:  A standard or principle upheld as indispensable for moral conduct, whether within a particular context or in general.