WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON; AND 20, SOUTH FREDERICK STREET, EDINBURGH. MDCCCLXIII. [The Right of Translation is Reserved.] PREFACE. THE motto of modern science is "the correlation of forces;" in other words, the unity of the powers which affect our senses. The present investigation is an attempt to carry that conception one step further, by showing a unity between the power manifested in the phenomena of sense, and the power exercised in the operations of thought. The method used in the investigation is, (1) to examine the process of thought in our own minds; (2) to follow its results through the great series of metaphysical systems evolved by the activity of Aryan thought, from the days of Thales to our own; (3) to compare this process with the results of the study of nature in their great outlines, as they are presented to us by modern science; and thus to establish the unity sought, as the most reasonable explanation of all the phenomena known to us. It will be obvious that in this operation we must touch upon questions of morals and religion, as well upon those concerning logic or physics. But the connexion of these topics, though long eschewed by modern inquirers, is plainly forced upon us by the advance of physical research. To say nothing of geology, take Professor Tyndall's eloquent enumeration, in his "Lectures on Heat," of the effects of solar action; or Sir John Herschel's picture of the benevolence associated with gigantic power |