In the youthful Dutch universities the effect of the essays was greater.
He soon, however, turned his attention to metaphysics and psychology, and for the North American Review and later for the National he wrote philosophical essays on the lines of Mill, Darwin and Spencer.
In 1697 appeared the first volume of his Essays on Several Moral Subjects, to which a second was added in 1705, and a third in 1709.
The first series contained six essays, the most notable being that "On the office of a Chaplain," which throws much light on the position of a large section of the clergy at that time.
The Geometry of Descartes, unlike the other parts of his essays, is not easy reading.