The aim of this essay is to show that any attempt to define theoretical limits to the proper scope of the criminal law must fail. In Chapter 1 an attempt is made to refute the Wolfenden Committee's contention that society must recognise 'a realm of private morality and immorality which is … not the law's business.' In so far as his arguments also pursue this aim Lord Devlin' s thesis is defended but no attempt is made to defend all that he said. Briefly, the argument advanced asserts that, if it is accepted that any society has the right to take whatever steps it considers necessary to ensure its continued survival then no jurisdictional barrier, such as that proposed by the Wolfenden Committee can be erected, owing to the public nature of all conduct. In other words, if by ' private morality and immorality ' is meant ' private behaviour in matters of morals' then there is no sphere of morality which can be distinguished on the ground that it has no public effect. The argument that there can be no theoretical limits placed on the proper scope of the law does not commit one to holding that all immoral conduct ought to be prohibited by law but rather that any immoral conduct may justifiably be prohibited.