Algernon Sidney, executed in 1883 as an alleged consirator in the Rye House Plot
During the later part of the 17th century religion was still cause for controversy, but people were not put to death purely on the grounds of their religious beliefs. Algernon Sidney is remembered as a martyr for another kind of belief - republicanism - though that belief was grounded partly in his religious convictions (i.e., that God intended his creatures to be free, not subject to the arbitrary dominion of an earthly ruler), and in any case the ostensible reason for his death was his alleged involvement in a plot to kill the king (Charles II).
The Rye House Plot was motivated, in part, by religious feeling. In 1881 Charles had dissolved Parliament and so stymied an attempt to exclude his younger brother, James (who had converted to Catholicism in 1669) from acceding to the throne after his death. Anti-Catholic sentiment was strongly opposed to the accession of a Catholic king, and also to the Catholic sympathies that Charles's action appeared to reveal. This led to the Rye House attempt to assassinate Charles, though there is speculation that there never really was a plot and the whole episode was concocted by the king and the Tories to throw the Whig party into disarray. In this it succeeded admirably; two prominent Whigs, Sidney and William, Lord Russell, were executed and a third, Ashley Cooper, Lord Shaftesbury, fled the country. (See here for an account of the Rye House Plot.)
One of the more curious aspects of Sidney's trial - along with the fact that he was convicted on extremely shaky evidence - was an unpublished manuscript, written by him, that was brought forward as evidence. This was a work he had been writing since 1880, expounding his belief in republicanism. It was claimed that the author of such a work was clearly capable of regicide. This was quite unfair, as can be seen from the following account of an episode at the end of the Puritan Revolution:
In January 1649 he [Sidney] was appointed - in his absence and against his wishes - as one of the Commissioners for the trial of Charles I. He approved of the deposition and trial of the king, but opposed his execution. In the event, he played no part in the proceedings, retiring to Penshurst until sentence had been passed.
Sidney's manuscript was published some fifteen years after his death, and it is this book that is shown here.
Discourses Concerning Government, by Algernon Sidney, Son to Robert Earl of Leicester, and Ambassador from the Commonwealth of England to Charles Gustavus King of Sweden. Published from an Original Manuscript of the Author (London, 1698; fol., pp. 462 + ). A very good copy, in an early binding (rebacked), of the first edition of Sidney's work.