He was the fifth and youngest son of Sir John Osborne of Chicksands Priory, Shefford, Bedfordshire, by his wife Dorothy, daughter and coheiress of Richard Barlee of Effingham Hall, Essex.
Coming to London as a youth, he hung about the court and attracted the notice of William Herbert, 3rd Earl of Pembroke, who made him his master of the horse.
After residing for a time at North Fambridge, Essex, he moved in about 1650 to Oxford to supervise the education of his son, John, and there printed a series of historical, political, and ethical tracts.
After the publication of his Advice to a Son in 1656, he gained a wide reputation, and paid many visits to London and reckoned the philosopher Thomas Hobbes among his friends.
In Osborne's day his Advice to a Son found admirers among the young scholars at Oxford, but the clergy detected atheism in its vague references to religion, and denounced its evil influence.
Miscellany of sundry Essays, Paradoxes, Problematical Discourses, Letters, and Characters, together with political Deductions from the History of the Earl of Essex,' London, 1659.
The collective edition of 1673 was brought to the notice of the House of Lords on 13 March 1676, on the ground that its incidental vindication of a republican form of government in England rendered it a seditious and treasonable publication.
[1] Osborne has also been credited, apparently wrongly, with Private Christian's non ultra, or a Plea for the Layman's interpreting the Scriptures, Oxford, 1650, (anon.
); with A Dialogue of Polygamy (London, 1657), translated from the Italian of Bernardino Ochino by 'a person of quality', and dedicated to the author of the Advice; and William Sprigge's A modest Plea for an equal Commonwealth against Monarchy.