 Book Three and the first part of Book Four develop Godwin’s case against existing theories of government, in each case making his case by drawing on his opening argument that there is no intrinsic limit on the development of human understanding and enlightenment. The philosophical underpinning for this argument is given in the second half of Book Four where Godwin examines the character of truth and its relationship to virtue and goes on to discuss arguments relating to freedom of the will, the doctrine of philosophical necessity, and the character of moral motivation. He shows that men are capable of recognising truth, and that, because mind acts as a real cause, they will act on it when they perceive it clearly. Nothing beyond the perception of truth is required to motivate our compliance with moral principles. It is this which justifies the description of Godwin’s position as “rationalist”, and it is on this point—the motivating power of reason—that later editions show a degree of retraction. One possible source for the position is Richard Price’s Review of the Principal Questions of Morals (1756), but it is noteworthy that Godwin himself later identified this “error” as a function of his Sandemanianism. In Political Justice, however, Godwin builds his argument on necessarian foundations laid by David Hartley and Joseph Priestley, albeit he develops their position by insisting that mind is the medium within which sensations, desires, passions and beliefs contend—so that we should understand the conflict between passion and reason as one of contending opinions. Such contention can be assessed impartially by the mind which will assess the true value of each claim and act on the judgment.