In this essay, which was written around 1785 but never published in his lifetime, Bentham examines the justifications given for the criminalisation of so-called "unnatural offences", principally the sexual offences of sodomy, bestiality and masturbation, and the severe punishments which attached to these crimes. He argues that there is little or no evidence that they harm either individuals or society and that there is no possible justification for harsh punishments imposed by the law.
He systematically works through the reasons that have been offered in support of these crimes by a series of distingushed writers, from William Blackstone, to Montesquieu to Voltaire, and dismisses them in turn as riddled with inconsistencies and prejudices and having no possible rational basis.
Thus, there is no evidence that the conduct produces pain; rather it produces pleasure. It cannot be an offence against security or the peace (Blackstone), if it is practised with consent. It cannot hurt the population (Voltaire), or rob women of their rights (!) or be harmful to marriage. And indeed, he asks, if homosexual sex is regularly practised on what basis can it be termed unnatural? The justification for such offences, he concludes seems to lie in a hatred of pleasure, rather than in any possible harm caused by the conduct itself, a position which has been set up by the "prejudices of false philosophy and the terrors of a false religion". In place of this, he argues that on the principle of utility he argues that there is no justification for these offences (although he does recommend "domestic discipline" as a remedy for for the pernicious and enervating effects of masturbation).
proposes a new scheme for the classification of criminal laws that would be consistent with his utilitarian principles (see ch.16). In place of the categories of the common law he proposed a more rational schema based around the interests to be protected by the law, moving from offences against individuals (person, reputation) to objects associated with persons (such as property), to various kinds of public offences (including offences against the positive increase of the national felicity...). And he sought to examine existing laws to see how they would fall within his new classification - either being reclassified or abandoned altogether.