Firmin was born at Ipswich some time in June 1632, and died of typhoid fever in London on 20 December 1697. After apprenticing with a London mercer, Firmin established his own mercery in Lombard Street, probably in 1655. He made the shop into a prosperous business, and in 1676 handed over the management of it to his nephew so that he could devote more time to charitable work. In 1673 he was appointed a governor of Christ's Hospital; he lost this post briefly thanks to his opposition to James II, but was restored on the accession of William and Mary. In 1693 he became a governor of St Thomas's Hospital. He became interested in the welfare of prisoners, and worked to alleviate conditions in some of the harshest prisons.
From The Biographical Dictionary of British Economists in Oxford Reference.