  No doubt, the new logic emerging in the second half of the 19th century was created in a Leibnizian spirit. The essentials of Leibniz’s logical and metaphysical program and of his ideas concerning a logical calculus were available at least since the 1840s. Erdmann’s edition of the philosophical works and Trendelenburg’s presentation of Leibniz’s semiotics were the most important steps towards the further reception of Leibnizian ideas among mathematical logicians at the end of the 19th century. As soon as these logicians became aware of Leibniz’s ideas, they recognized Leibniz’s congenial affinity and accepted his priority. But the logical systems had basically been already established. Therefore there was no initial influence of Leibniz on the emergence of modern logic in the second half of the 19th century.