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.
Among his essays may be mentioned The Evolution of Self-Consciousness and two articles published in 1871 on the Genesis of Species.
His essays were collected and published by C. E.
Among his other publications may be mentioned Essays, Theological and Literary (1871; revised 1888), and Criticisms on Contemporary Thought and Thinkers (1894); and his opinions may be studied compendiously in the selections from his Spectator articles published in 1899 under the title of Aspects of Religious and Scientific Thought.