Looking for a definition of my subject, I find in my learned and lamented friend Professor Dicey's introduction to the second edition of his Law and Public Opinion in England, written in 1914, a sentence which will serve better than any definition of my own. “Since 1859”—the date of Mill's Essay on Liberty—“ almost every event which has happened has diverted public attention to the extreme difficulty, not to say the impossibility, of drawing a rigid distinction between actions which merely concern a man himself and actions which also concern society.” That is a clear statement in untechnical terms of the facts underlying the formal distinction between Public and Private Law, and of the fact that the relations of the two classes of actions and of the rules of law dealing with them have become in our own time, and are still becoming, more and more intimate and complex. It has more than once been observed of late that Public Law is encroaching on Private Law. Perhaps it has not been sufficiently noted that this process by no means obliterates the distinction between them, but on the contrary makes it all the more needful to bear it in mind. Confusion and trouble must arise when private rights arising out of legal or administrative rules established with a primary view to the public weal are treated as if they were matters of merely private interest, and when the framers or administrators of measures designed for the public good ignore the various ways in which private rights will be affected.