Who Was Henry Marten?

Another question related to this post is "what is reformed Protestantism?"

I was involved in the comments section at the Law and Liberty site on BRUCE P. FROHNEN's latest. One learned commenter stressed the "reformed Protestant" element in the development of the concept of "liberty" in America and Great Britain.

Though, the commenter seemed to have a very broadly defined understanding of reformed Protestant Christianity. They asserted it encompassed the Arian and Socinian doctrines. As they put it:

... I don’t know that [Roger] Williams ever expressed an opinion about Servetus but non-trinitarinism has been a feature of Christianity since about 300 AD and Arianism was the Christianity of the Goths and Theodoric the Great who conquered Italy in 493. Further, Socinianism had been in the air in England and since 1610, it was part of the Polish Brethren’s belief system in the 1560s. It is a common place observation that rationalist and biblical literalist Reformed christians like Newton, Henry Marten, John Adams, Benjamin Franklin and Thomas Jefferson exhibited a marked tendency [toward] non-trinitarianism.

I replied that I didn't know anything about Henry Marten and that very few people associate theological unitarianism with the label “biblical literalist Reformed christian[ity].” Though, yes, arguably it was part of the theologically liberal (for the time) wing of “Protestant Christianity.”

So the commenter noted:

Henry Marten was perhaps the most radically republican member of the Long Parliament. He was John Lilburne’s best connection in Parliament after Cromwell put Lilburne on trial for treason in 1649. Lilburne appeared pro se and told the jury they were final deciders of both the law and the facts. The jury acquitted Lilburne and the cheering spectators carried “Freeborn John” out of the courtroom on their shoulders.  

Like Col. Thomas Rainborowe’s brother, William, Marten was often called a Ranter. Here it is interesting to note that John Winthrop became Thomas and William Rainborowe’s brother-in-law in December 1647 when Winthrop married their widowed sister, Martha Coytmore, in Boston. Winthrop’s son, Stephen, had already been commissioned in the New Model Army. He rose quickly and died in Scotland a Lt. Colonel in what had formerly been Sheffield’s regiment of horse. Things might have been very different in both England and New England had Winthrop and Col. Rainborowe not died so young and so close together in 1648-49.

I briefly looked online for evidence of Marten's creed. This is what Wiki noted:

Although a leading Puritan, Marten enjoyed good living. He had a contemporary reputation as a heavy drinker and was widely said to be a man of loose morals.^[2] According to John Aubrey he was "a great lover of pretty girls to whom he was so liberal that he spent the greatest part of his estate" upon them.^[10] In the opinion of King Charles I he was "an ugly rascal and whore-master".^[11] He married twice (to Elizabeth Lovelace and Margaret Staunton (née West) but had an open and lengthy relationship with Mary Ward, a woman not his wife, by whom he had three daughters.^[12] Ward ultimately was to remain with him throughout his later imprisonment.^[4] His enemies branded him an atheist but his religious views were more complex, and influenced his position regarding the need to allow freedom of worship and conscience.^[13] His political views throughout his life were constant: he opposed one-man rule^[14] and was in favour of representative government. In 1643, even while the king was losing the First Civil War and Parliament's cause was beginning to triumph, Marten's republican sentiments led to his arrest and brief imprisonment.^[15] Thus for his time Marten was unusual in his political stance, being unashamedly in favour not of reforming the monarchy but of replacing it with a republic.^[16]