To judge of the source of writings by apparent varieties of style, and call in a different writer for every such variety, is to commit oneself to a very precarious rule. There are doubtless cases where the diversity of style is so marked that the inference is justified, but in these the evidence is unmistakably clear. Often the evidence against identity of authorship _appears_ very clear, while it is absolutely worthless. Suppose that three thousand years hence an English book should be found, consisting, first, of an eloquent exposition of a parliamentary budget; secondly, a scheme for Home Rule in Ireland; thirdly, a dissertation on Homer; and fourthly, essays on the "Impregnable Rock of Holy Scripture"--how convincingly might the critics of the day demonstrate, beyond possibility of contradiction, that the book could not be the work of the single man who bore the name of William E. Gladstone! In like manner, it might be made very plain that Milton could never have written both "L'Allegro" and "Il Penseroso," or "Paradise Lost" and the "Defence of the English People." Cowper could not have written "John Gilpin" and "God moves in a mysterious way." Samuel Rutherford could not have written his "Letters" and his "Divine Right of Church Government." Moreover, in the course of years a writer may change his style, even when his subject is the same. The earlier essays of Mr. Carlyle show no traces of that most quaint, terse, graphic style which became one of his outstanding characteristics in later years. Perhaps the most remarkable instance of change of style in a great writer is that of Jeremy Bentham. In Sir James Mackintosh's Dissertation prefixed to the _Encyclopædia Britannica_ (eighth edition) he says: "The style of Mr. Bentham underwent a more remarkable revolution than perhaps befell that of any other celebrated writer. In his early works, it was clear, free, spirited, often and seasonably eloquent.... He gradually ceased to use words for conveying his thoughts to others, but merely employed them as a short hand to preserve his meaning for his own purpose. It is no wonder that his language thus became obscure and repulsive. Though many of his technical terms are in themselves exact and pithy, yet the overflow of his vast nomenclature was enough to darken his whole diction."