My Parents had early given me religious Impressions, and brought me through my Childhood piously in the Dissenting Way. But I was scarce 15 when, after doubting by turns of several Points as I found them disputed in the different Books I read, I began to doubt of Revelation itself. Some Books against Deism fell into my Hands; they were said to be the Substance of Sermons preached at Boyle's Lectures. It happened that they wrought an Effect on me quite contrary to what was intended by them: For the Arguments of the Deists which were quoted to be refuted, appeared to me much Stronger than the Refutations. In short I soon became a thorough Deist.

Part I, p. 45 - The Autobiography (1817)