This thesis is an intellectual history of James Mill's political thought, which focuses on four specific topics: his ideas on parliamentary reform; on libel law, or the freedom of the press; education, or man's ability to utilise his reason; and on established religion, primarily in the form of Mill's attitude towards the Church of England. At face-value, the thesis' main aim is to contextualize in detail Mill's published writings on these four subjects (which comprise its four chapters) by virtue of comparing them with unpublished manuscript material present in his common place books, which were transcribed as part of this PhD project. Although the chapters are developed in such a way that they can be seen as independent studies of Mill's thought, there are of course more general themes which run through the thesis as a whole, as well as specific links between particular topics. One notable example is the notion that Mill employed ‘dissimulation' in his published writings, that is to say that he did not necessarily express in public the full extent of his ideas, because of a fear that their radical extent would attract intrigue or prosecution from the reactionary governmental or religious authorities in Britain. It is also prudent to note how Mill's well-documented intellectual influences are incorporated into the thesis. By this we are referring to the importance of the Scottish Enlightenment background to Mill's own education and upbringing near Aberdeen and in Edinburgh, and also the doctrine of Utilitarianism he adopted from Jeremy Bentham once in London. The particular nature of the material found in the common place books warrants a full re-evaluation of these influences, as well as an exploration of the possibility that additional influences beyond these two contexts have thus far been understated in studies of Mill. This suggests the value of the study to current Mill scholarship.