Many historians and philosophers of logic have claimed that during the 19th century, before Gottlob Frege's Begriffsschrift (1879), there was a long period of stagnation or even of decline in the field of logic. The aim of this book is to show that such an evaluation of 19th century logic is misdirected and needs to be corrected. A Hundred Years of Logical Investigations discusses both philosophical and mathematical efforts to reform logic in Germany from Kant's Kritik der reinen Vernunft (1781) up to Frege's Begriffsschrift (1879). Amongst others, J.F. Herbart, M.W. Drobisch, G.W.F. Hegel, F.A. Trendelenburg, R. Graßmann, and E. Schröder are discussed in addition to Kant and Frege with regard to their thoughts about the place, the task, and the justification of logic not only as a philosophical discipline, but also as a formal and fundamental theory of science.