This Article opens with a discussion of Thoreau's philosophy of civil disobedience and then examines the ideas of four modem legal philosophers, Joseph Raz, Kent Greenawalt, John Rawls, and Ronald Dworkin, on the subject. Next, the Article compares the respective thinking of all five men regarding the circumstances that would justify the use of civil disobedience. To facilitate the comparison as well as to make it more relevant to the reader, the Article examines five related contemporary illustrations involving situations in which the use of civil disobedience might arguably be morally justified. This Article concludes with some general thoughts on the circumstances justifying the use of nonviolent civil disobedience.