The first of the three books in which Reid set out the results of his labours appeared in 1764 under the title, Inquiry into the Human Mind on the Principles of Common Sense. The other two, Essays on the Intellectual Powers of Man and Essays on the Active Powers of Man, appeared twenty years later. In these books Reid had in view a more all-embracing purpose than in his first work. The achievement of this purpose, however, required a greater spiritual power than was granted to him. Comparing his later with his earlier work, Reid's biographer, A. Campbell Fraser, says: