John Sadler (of Warmwell, Dorset) (18 August 1615 – April 1674) was an English lawyer, academic, Member of Parliament, Town Clerk of London, Hebraist, Neoplatonist[1] and millenarian thinker, private secretary to Oliver Cromwell, and member of the Parliamentarian Council of State.
Ernestine van der Wall writes:[6] John Sadler (1615–1674) was a well-known London lawyer and constitutional theorist, and a good friend of Oliver Cromwell, at one time serving as his personal secretary.
During the 1650s he held several offices, being secretary to the Council of State and a member of the Committee for the Advancement of Learning and the Committee for Lunatics.The Hale Commission on law reform, headed from 1652 by Sir Matthew Hale, had Sadler as a leading lawyer, together with William Steele and John Fountain.
Maurice Vile writes Sadler's view of the executive function was, as we have seen, not our modern one, but in other respects his grasp of the principles of the doctrine of the separation of powers was clear.
[15] He believed that readmission would allow for the Jews to be converted to Christianity, which would hasten the new millennium (which he conceived as being a time of "more justice and more mercy" rather than being visited by Christ's "bodily presence").