Preparatory Principles is not a linear text in the conventional sense, but consists of a series of short passages on a variety of topics, whose themes are summarised in marginal headings. The material constitutes a philosophical commonplace book, compiled by Bentham in the mid-1770s, in which he worked out the foundational ideas for his new science of legislation. He then drew on this material when composing such works as A Fragment on Government and An Introduction to the Principles of Morals and Legislation. Inspired by such figures as John Locke and Claude Adrien Helvetius, Bentham developed an original ontological and epistemological basis for legal terminology, with the aim of replacing the traditional terminology of English law with that of universal jurisprudence. The work that dominates the text, in that Bentham returns to it time and time again in order to offer criticism of it, is William Blackstone’s Commentaries on the Laws of England. While unorganized and fragmentary, the material in Preparatory Principles constitutes a remarkable record of the evolving ideas of a major legal philosopher at a formative stage of his career.