The successful management of a prison, he says, "demands special knowledge and ability. This knowledge should first of all consist in a comprehensive general education, so that the head of a prison may be able to form a competent opinion in all those branches of knowledge which bear upon the punishment of crime. He thus stands on a footing of equality with his subordinates. If he is deficient in this knowledge he will not be able to carry out the sentences of the law efficiently, and the maintenance of his official authority will be encumbered with difficulties. He must also possess an understanding of the economic and social causes of crime as well as of its individual causes. An understanding of its economic and social causes supposes that he should be acquainted with the principles of sociology and political economy; an understanding of its individual causes supposes that he should know something of psychology. The historical, philosophic, and legal aspects of criminal jurisprudence as well as its formal contents ought not to be unknown ground. In the domain of prison science he should be thoroughly at home. He ought to be acquainted with the historical development of punishment by imprisonment, as well as with the nature of the various prison systems in existence among modern civilised communities. He ought to have a clear understanding of the aim and object of imprisonment, and be thoroughly cognisant of the legal and administrative arrangements by which it is effected, more especially those of his own State. He should possess a competent knowledge of all matters and regulations bearing upon prison administration, so that his own arrangements may be based upon a ripened judgment.