He was a native of Leicester, where he was born of poor parents early in the seventeenth century. On 4 July 1623 he was entered as a
sizar at
Emmanuel College, Cambridge, where he graduated B.A. in 1627, M.A, in 1631. Lack of funds led him to leave Cambridge and teach a school, apparently in London. He was chosen lecturer at
St. Martin's, Ludgate, and became chaplain to
Algernon Percy, 10th Earl of Northumberland. In 1642 he was presented by
William Laud to the rectory of
Allhallows, Bread Street; Laud made this presentation out of courtesy to Northumberland, and complained that, nonetheless,
Henry Montagu, 1st Earl of Manchester, had written to pressure him, commanding him in the name of the House of Lords to give the benefice to Seaman. In 1643 he was nominated a member of the
Westminster Assembly and he was a regular attendant, saying there on 18 February 1645, "In no institution did God go against nature." On 6 November 1645 Seaman was placed on the committee of accommodation designed by parliament to arrange terms for the comprehension of the Independents; the project fell through, as the independents rejected the planned comprehension and insisted on
religious toleration. He was one of the
remonstrants (26 May 1646) against the toleration of 'separate congregations,' and maintained in the Westminster Assembly the divine right of the presbyterian discipline. At the second meeting (8 November 1647) of the provincial assembly of London, Seaman, a member of the first London classis, was moderator. In September–November 1648 he was one of the four presbyterian divines commissioned to the
Isle of Wight to recommend their case to
Charles I in discussion with the king, aided by episcopalian divines; Charles complimented Seaman on his ability. In January 1649 he signed the
Vindication drawn up by
Cornelius Burges, protesting against the king's trial. He proceeded D.D. in 1649. In 1653 he was vice-chancellor of Cambridge, and in 1654 was appointed by
Oliver Cromwell, one of the Visitors of his university. On the
English Restoration, John Cosin was restored as Master of Peterhouse on 3 August 1660. Seaman held aloof, with
William Jenkyn and a few others, from the negotiations with
Charles II in the presbyterian interest, and was looked upon as an uncompromising man, whom it was useless to tempt with offers of preferment. He resigned his benefice in consequence of the
1662 Uniformity Act; his successor, Risden, was appointed on 26 August 1662. On the passing of the
Five Mile Act 1665,
Richard Baxter drew up a statement of reasons for not taking the oath which exempted from its operation; Seaman persuaded him to abstain from publishing it, and recommended a policy of 'silent patience.' He privately ministered to a congregation of his former parishioners, preached publicly after the
Great Fire of London of 1666, and after the indulgence of 1672 built a chapel in Meeting-house Yard, Silver Street, Wood Street,
Holborn.
Anthony à Wood, who knew him personally, refers to him respectfully as "a learned nonconformist." He died in Warwick Court, Newgate Street, about 9 September 1675; Jenkyn preached his funeral sermon on 12 September; an elegy on his death was issued (1675) as a broadsheet. His library of 5,000 books was sold at auction, the first time an auction of this kind had been held in England. ==Works==