Explicating John Donne's ‘doubt wisely’, this essay argues for the theological and psychological sophistication of Richard Hooker's distinction of wise from unwise doubt and shows why this led him to support compulsory adherence to the Church of England. Framed by consideration of how his ideas were adopted by Thomas Browne's Religio Medici (1643), it explores Hooker's thinking on what is certain in itself and where we can properly doubt. If true, the revealed character of God and the consequent acknowledgement of God as faithful to his elect, is true by necessity, or definition, and may be held with certainty of adherence: whatever my emotional state, adhering is proof that I have not denied my faith and am therefore sincere in my profession. It is wise to doubt the absolute importance of issues such as the right definition of Christ's presence in the sacrament, the God-given character of any specific Church order, and assumptions about the spiritual state of any other baptized person. We cannot, however, be doubtful about the Church to which allegiance is commanded by law. For Hooker, legal enforcement of conformity is a pastoral good: it enables the unsure to establish a practice likely to offer them some anchorage for fluctuating convictions and ‘affections’.