Laud, now archbishop of Canterbury, was not a little solicitous about Chillingworth's reply to Knott, and at his request, as "the young man had given cause why a more watchful eye should be held over him and his writings," it was examined by the vice-chancellor of Oxford and two professors of divinity, and published with their approbation in 1637, with the title _The Religion of Protestants a Safe Way to Salvation_. The main argument is a vindication of the sole authority of the Bible in spiritual matters, and of the free right of the individual conscience to interpret it. In the preface Chillingworth expresses his new view about subscription to the articles. "For the Church of England," he there says, "I am persuaded that the constant doctrine of it is so pure and orthodox, that whosoever believes it, and lives according to it, undoubtedly he shall be saved, and that there is no error in it which may necessitate or warrant any man to disturb the peace or renounce the communion of it. This, in my opinion, is all intended by subscription." His scruples having thus been overcome, he was, in the following year (1638), promoted to the chancellorship of the church of Sarum, with the prebend of Brixworth in Northamptonshire annexed to it. In the great civil struggle he used his pen against the Scots, and was in the king's army at the siege of Gloucester, inventing certain engines for assaulting the town. Shortly afterwards he accompanied Lord Hopton, general of the king's troops in the west, in his march; and, being laid up with illness at Arundel Castle, he was there taken prisoner by the parliamentary forces under Sir William Waller. As he was unable to go to London with the garrison, he was conveyed to Chichester, and died there in January 1644. His last days were harassed by the diatribes of the Puritan preacher, Francis Cheynell.
Besides his principal work, Chillingworth wrote a number of smaller anti-Jesuit papers published in the posthumous _Additional Discourses_ (1687), and nine of his sermons have been preserved. In politics he was a zealous Royalist, asserting that even the unjust and tyrannous violence of princes may not be resisted, although it might be avoided in terms of the instruction, "when they persecute you in one city, flee into another." His writings long enjoyed a high popularity. The _Religion of Protestants_ is characterized by much fairness and acuteness of argument, and was commended by Locke as a discipline of "perspicuity and the way of right reasoning." The charge of Socinianism was frequently brought against him, but, as Tillotson thought, "for no other cause but his worthy and successful attempts to make the Christian religion reasonable." His creed, and the whole gist of his argument, is expressed in a single sentence, "I am fully assured that God does not, and therefore that men ought not to, require any more of any man than this, to believe the Scripture to be God's word, and to endeavour to find the true sense of it, and to live according to it."