The present edition of The Book of Fallacies is the first that follows Bentham's own structure for the work, and includes a great deal of material, both in terms of the fallacies themselves and the illustrative matter, that previous versions of the work have omitted. The fallacies that concerned Bentham were not logical errors of the sort identified by Aristotle, or commonplace misunderstandings of matters of fact, but arguments deployed in political debate, in particular in the British Parliament, in order to prevent reform. Bentham not only identified, described, and criticized the fallacious arguments in question, which were all characterized by their irrelevancy, but explained the sinister interests that led politicians to employ them and their supporters to accept them. By exposing these political fallacies, Bentham hoped to prevent their employment in future, and thereby to place political debate on its only proper ground, namely considerations drawn from the principle of utility.