Rejected by the Sheffield dissenters as 'too gay and airy' (Yates), in September 1758 Priestley became minister at Nantwich, Cheshire. The congregation was very small, chiefly consisting of 'travelling Scotchmen,' and 'not one of them was at all Calvinistical.' He wrote few sermons, but established a flourishing school, never giving 'a holiday on any consideration.' His school and private tuition occupied him from seven in the morning till seven at night. Yet he learned to play the flute, 'as the easiest instrument,' and congratulated himself on having no ear, being thus 'more easily pleased.' He formed a friendship with Edward Harwood [q. v.], and was intimate with Joseph Brereton (d. 1787), vicar of Acton, near Nantwich, who gave him a telescope 'made with his own hands' (Works, xix. 306).
Aikin's promotion to the divinity tutorship at Warrington Academy was followed by Priestley's appointment (September 1761) to the tutorship there in languages and belles-lettres. He would have preferred the chair of natural philosophy, held by John Holt [see Horsley, John]. In his own department he introduced public exercises in English and Latin, and gave three courses of historical lectures, dealing especially with constitutional history, for students designed for 'civil and active life.' These lectures, published in 1788, were recommended at Cambridge by John Symonds [q. v.], professor of modern history. His 'Essay on Government,' written at Warrington, and published in 1768, contains the sentence to which Jeremy Bentham [q. v.] considered himself indebted for the phrase 'the greatest happiness of the greatest number.' Edinburgh University conferred on him the diploma of LL.D. (4 Dec. 1764).
Priestley had been ordained on 18 May 1762 at Warrington. On 23 June in the same year he married, at Wrexham, Mary, only daughter of Isaac Wilkinson, of Plas Grono, ironmaster at Bersham, near Wrexham, afterwards of Bristol; her age was eighteen. She was a woman of sound culture and strong sense. Before his marriage Priestley described her to his brother as 'very orthodox,' but Timothy, on making her acquaintance, decided that she was 'no dox.' At the wedding the bride was given away by Priestley's pupil, Thomas Threlkeld [q. v.], an absent-minded scholar, who, finding a Welsh bible in a pew of the parish church, forgot his duty in its perusal (Barnes). His marriage led Priestley to project a 'widows' fund' for protestant dissenters of Lancashire and Cheshire. The scheme was launched on 16 May 1764, and produced a valuable benefit society, since become wealthy.
Priestley spent a month of every year in London, where he met Franklin. His life at Warrington was 'singularly happy.' The tutors worked harmoniously, and had their Saturday club for graver converse; for lighter recreation there was a coterie of anonymous verse writers, whose pieces were dropped into Mrs. Priestley's workbag (Bright). Some of Priestley's own verses first roused the poetic gift in Aikin's only daughter (afterwards known as Anna Lætitia Barbauld) [q. v.] But the academy did not flourish; Priestley was cramped for means (his salary was 100/. with a house, in which he took a few boarders at 15/. apiece), and his wife's health failed. Accordingly he welcomed a call to the ministry of Mill Hill Chapel, Leeds, and removed thither in September 1767. His salary, though exceeding that of most dissenting ministers at that date, was only a hundred guineas and a house, but his time was at his own disposal.
He devoted his weekdays to his studies, and wrote few discourses, making no secret of his habit of exchanging sermons with his friends (Monthly Repository, 1818, p. 94); but he carefully instructed his flock in graduated classes for systematic catechising, a practice neglected by the liberal dissenters of that day. For ten years his theology had remained stationary. He now read Lardner 'On the Logos,' published in 1759, and became what is called a Socinian,' a development which much stimulated his controversial activity. As an organ of critical inquiry he projected (1768) and set on foot (1769) the 'Theological Repository,' which was published at irregular intervals till 1788. He offended public opinion by inviting, without success, the co-operation of deists; he aspired to make his magazine an open platform for the discussion of all subjects relating to biblical science. His first polemical piece (1769) was in reply to an attack by Henry Venn [q. v.] His propagandist publications began with his 'Appeal' (1770), the most successful of his tracts, written in view of the progress of methodism among dissenters.
Priestley's ecclesiastical views retained the impress of his early training among independents. The decay of church organisation and the neglect of the sacraments among liberal dissenters concerned him; he proposed remedies in his address (1770) on church discipline, and his discourse (1782) on the constitution of a Christian church. He upheld the autonomy of the particular congregation, and was 'for increasing the number of sects rather than diminishing them:' hence his spirited 'Remarks' (1769) on Blackstone, who had classed nonconformity