The Collapse of the Harm Principle Redux: On Same-Sex Marriage, the Supreme Court's Opinion in United States v. Windsor, John Stuart Mill's Essay On Liberty (1859), and H. L. A. Hart's Modern Harm Principle

Bernard E. Harcourt, Columbia Law School


In an article published in 1999, titled The Collapse of the Harm Principle, I argued that the harm principle, originally articulated in John Stuart Mill’s essay On Liberty (1859), had collapsed under the weight of its own success and no longer serves, today, as a limiting principle on the legal enforcement of morality. Several readers raised forceful questions about the relationship between Mill’s original essay and the harm principle, as well as about the continuing vitality of Mill’s argument. In this article, I return to my original argument to draw an important distinction and clarify a central point. The argument in The Collapse of the Harm Principle can be slightly restated and, I believe, continues to shed light on contemporary debates over the legal regulation of morality: Today, the hegemony of the modern harm principle, developed by liberal legal thinkers at mid-twentieth century, continues to generate a proliferation of harm arguments, and the competing claims of non-trivial harms have effectively neutralized the limiting function of the harm principle. I then demonstrate the continued vitality of the argument by exploring the recent Supreme Court decision on same-sex marriage, United States v. Windsor, which, I argue, reflects perfectly the collapse of the harm principle.