This thesis will examine the ideas on the mind and its disorders in British medicine from around 1660 to about 1780, corresponding roughly to 'the long eighteenth century' of Roy Porter or 'l'âge classique' of Michel Foucault. The period starts with the medicine of the Scientific Revolution, and ends just before the 'Psychiatric Revolution' started. It is concerned with the pre-history of British psychiatry during the Enlightenment. Psychiatry was not an independent discipline during this period, so medical ideas about the human mind and madness will be considered in the schemes of general medicine. Changes in the understanding of madness will be traced with reference to those in general physiology and pathology. Major medical writers to be examined include: Thomas Willis, Archibald Pitcairn, Richard Mead, Nicholas Robinson, George Cheyne, William Battie, John Monro, and William Cullen. The interplay between medical ideas on the mind and madness, and contemporary philosophical and religious thinkings will also be examined. The influence of the philosophies of Descartes, Locke, Hume and some others upon psychiatric thinking will be looked at. Here the relation was often delicate. Medical writers did not simply adopt philosophical and religious frameworks of the mind, but more often tried to differentiate the scope of medicine from that of metaphysics, especially in the earlier part of the eighteenth century. As the century went on, there was a shift toward fusing philosophical discourse on the mind and medical discourse on the body, and hence a shift toward psychological understanding of madness. David Hartley and William Cullen represented the trends.