Through his published sermons, he entered the theological debate that flourished around the Arian controversy, and the doctrinal question as to Man's essential nature.
He contested the Deism of the Norwich rationalists in the early enlightenment, and challenged the Trinitarian conventional wisdoms about the seat of humanity and its origins.
He was taught classics at Bolton and trained for the ministry in the Manchester dissenting academy of John Chorlton and James Coningham.
He carried with him his father's theology, but at his ordination, he declined subscription, not from particular scruples, but on general principles; as a result, many of the neighbouring ministers refused to concur in ordaining him.
[1] In 1719, when the Salters' Hall conference had made the Trinitarian controversy a burning question among dissenters, Bourn, hitherto Athanasian, addressed himself to reading Samuel Clarke and Daniel Waterland, and accepted the Clarkean scheme.
[1] Bourn was harassed by John Ward of Sedgley Park, who sought to compel him to take and maintain a parish apprentice.
[1] Bourn had a hot temper, and was not averse to controversy, repelling a field-preacher, or attacking quakers in their own meeting-house; and with difficulty was held back by his friend Job Orton from replying on the spot to the doctrinal confession of a young independent minister, who was being ordained at the New Meeting, lent for the occasion.