The first major collection of Boyle's writings to be published since Thomas Birch's eighteenth-century edition of his works presents material hitherto available only in the archives of the Royal Society. This edition of Boyle's Aretology (the study of moral virtue) and other moral essays from the late 1640s offers the intellectual and religious origins of Boyle's most vital themes. John T. Harwood also includes two essays on moral topics, Of Sin and Of Piety; a sample of Boyle's private meditations, Joseph's Mistress; a short essay, Of Time and Idleness; and two guides to private meditation, The Dayly Reflection and Of Thoughts. Harwood concludes the volume with a previously unpublished account of about seven hundred books in Boyle's library at the time of his death.