One of the most prominent theologians in England during his lifetime, Owen was a prolific author who wrote articles, treatises, Biblical commentaries, poetry, children's catechisms, and other works.

Owen's support for the parliamentarians during the English Civil War resulted in him preaching a sermon before parliament on the day following the execution of Charles I, and later serving as an aide and chaplain to Oliver Cromwell.

A Puritan by upbringing, in 1637 Owen was driven from Oxford by Laud's new statutes, and became chaplain and tutor in the family of Sir Robert Dormer and then in that of Lord Lovelace.

At the outbreak of the English Civil War he sided with the parliament, and thus lost both his place and the prospects of succeeding to his Welsh Royalist uncle's fortune.

His doubts were removed by a sermon preached by a stranger in the church of St Mary Aldermanbury where he had gone intending to hear Edmund Calamy the Elder.

At Fordham he remained engrossed in the work of his parish and writing only The Duty of Pastors and People Distinguished until 1646, when, the old incumbent dying, the presentation lapsed to the patron, who gave it to someone else.

In this sermon, and in his Country Essay for the Practice of Church Government, which he appended to it, his tendency to break away from Presbyterianism to the Independent or Congregational system is seen.

[3] Another sermon preached on 29 April, a plea for sincerity of religion in high places, won not only the thanks of parliament but the friendship of Oliver Cromwell, who took Owen to Ireland as his chaplain, that he might regulate the affairs of Trinity College, Dublin.

[3] During his eight years of official Oxford life Owen showed himself a firm disciplinarian, thorough in his methods, though, as John Locke testifies, the Aristotelian traditions in education underwent no change.

With Philip Nye he unmasked the popular astrologer, William Lilly, and in spite of his share in condemning two Quakeresses to be whipped for disturbing the peace, his rule was not intolerant.

While little encouragement was given to a spirit of free inquiry, Puritanism at Oxford was not simply an attempt to force education and culture into "the leaden moulds of Calvinistic theology."

During his Oxford years he wrote Justitia Divina (1653), an exposition of the dogma that God cannot forgive sin without an atonement; Communion with God (1657), Doctrine of the Saints' Perseverance (1654), his final attack on Arminianism; Vindiciae Evangelicae (1655), a treatise written by order of the Council of State against Socinianism as expounded by John Biddle; On the Mortification of Sin in Believers (1656), an introspective and analytic work; Schism (1657), one of the most readable of all his writings; Of Temptation (1658), an attempt to recall Puritanism to its cardinal spiritual attitude from the jarring anarchy of sectarianism and the pharisaism which had followed on popularity and threatened to destroy the early simplicity.

As vice-chancellor he acted with readiness and spirit when a Royalist rising in Wiltshire broke out in 1655; his adherence to Cromwell, however, was by no means slavish, for he drew up, at the request of Desborough and Pride, a petition against his receiving the kingship.

In 1658 he took a leading part in the conference of Independents which drew up the Savoy Declaration (the doctrinal standard of Congregationalism which was based upon the Westminster Confession of Faith).

In 1661 the celebrated Fiat Lux, a work by the Franciscan friar John Vincent Cane, was published; in it, the oneness and beauty of Roman Catholicism are contrasted with the confusion and multiplicity of Protestant sects.

The Conventicle and Five Mile Acts drove him to London; and in 1666, after the Great Fire, he, like other leading Nonconformist ministers, set up a room for public service and gathered a congregation, composed chiefly of the old Commonwealth officers.

From this time to his death he was occupied with continual writing, disturbed only by suffering from kidney stones and asthma, and by the absurd charge of being concerned in the Rye House Plot.