Letters 279–307 show Shaftesbury living in Rotterdam for a year of recuperation and retirement. Although overshadowed by family troubles, the retreat, besides improving his physical health, offered the seclusion needed for sustained attention to his inward constitution, for rigorous philosophical training, as also for work on ›The Sociable Enthusiast‹. Not always wholly withdrawn, he felt able choose his company and decline invitations, seeing, for example, Pierre Bayle and new protégés, but not visiting the Prussian court. The months following his return to England (letters 308–335) were marked anew by ill health, but also by an inner energy that allowed him privately to voice scathing criticism of the (by then) late John Locke. Supplementary material is included in the form of appendices.