These four treatises illustrate four different aspects of Paracelsus' work. The first gives a passionate justification of his character, activities, and views, and gives a picture of the man and his basic character. The second treatise is a study of the disease of miners, with whom Paracelsus had spent a great deal of time. Then follows a treatise on the psychology and psychiatry of Paracelsus. Written at a time when mental diseases were beginning to be studied and treated by physicians, this essay anticipates a number of modern views. The last essay, entitled "A Book on Nymphs, Sylphs, Pygmies, and Salamanders, and on the other spirits," is a fanciful and poetic treatment of paganism and Greek mythology, as well as a good sample of Paracelsus' philosophy and theology. Together these essays show one of the most original minds of the Renaissance at the height of his powers.