In most discussions of civil disobedience, certain characteristics are offered as essential to an act of justifiable civil disobedience, or sometimes to any act of civil disobedience. Among these one of the most frequently mentioned is nonviolence. Some thinkers, like Bedau and Wasserstrom, require an act to be nonviolent before they will even count it as an act of civil disobedience; the very concept for them includes the notion of nonviolence. Others, like Stuart Brown, Rex Martin and Michael Bayles, admit the possibility of a violent act of civil disobedience; but hold that, though nonviolent civil disobedience is justifiable, violent civil disobedience is not justifiable.