REVIEWS OF BOOKS.
This first volume of Professor Erdmann's Logic is extremely rich in content, and, like several other recent logical treatises, such as Sigwart's and Wundt's, it defies a summary judgment, and must in the main be tested by long usage. The noted student of Kant's philosophical development does here no injustice to his well-earned reputation for minuteness and carefulness of scholarship. Where close examination is required, Erdmann does not spare pains, nor does he fear to weary his readers. On the other hand, breadth of view is secured by two devices, not unfamiliar in themselves, but here carried out with great industry. The one device is that of the historical comparison of logical doctrines, the other that of great variety in the choice of concrete examples of logical forms, principles, and processes. The historical comparisons are, to be sure, very briefly set forth, in summary paragraphs, usually placed at the conclusion of each new positive statement of Erdmann's own views. The examples, on the other hand, are sometimes almost capriciously multiplied. Yet everywhere a marvellous range of literary and historical knowledge is shown, and logical authors long since almost forgotten are brought down from dusty shelves to illuminate, often with surprising vividness, our author's argument. The recent progress of logical discussion, since Ueberweg and Lotze, is also borne in mind; nearly all the "burning questions" of the logic of the past two decades are touched upon; our author has his views concerning the nature of negative propositions, concerning the "impersonals," concerning "existential" judgments, concerning hypothetical judgments, in short concerning the favorite problems of modern continental logic in general.
Characteristic for our author's whole attitude is, meanwhile, his position with regard to the "Algebra of Logic," which Schroeder has recently so well introduced to German readers. Erdmann postpones until a later volume (so I understand his statement on p. 431) "die grundsätzliche Auseinandersetzung mit diesem Formalismus, der dem wissenschaftlichen Gebrauch des Denkens fremd ist, und fremd bleiben muss," but he everywhere condemns its method. Boole's algebraic formulation of the principle of contradiction, in its relation to the formula
