 In The Analyst of 1734 Berkeley launched his most sustained and sophisticated critique of infinitesimals and the whole metaphysics of the calculus. Addressed To an Infidel  Mathematician,[24]  the tract was written with the avowed purpose of defending theology against the scepticism shared by many of the mathematicians and scientists of the day. Berkeley’s defense of religion amounts to the claim that the reasoning of mathematicians in respect of the calculus is no less flawed than that of theologians in respect of the mysteries of the divine.