Leibniz is known to the wide public and to many scholars mainly as a logician and mathematician, and as the creator of a fascinating but strange metaphysical system. In these, as well as in other fields, his remarkable innovations were achieved by painstaking efforts to establish a fruitful critical dialogue with the leading contemporary thinkers. He was no less important, however, in his practical endeavor to bring opponents to negotiate reasonable solutions to key political and religious conflicts of his time. Both his theoretical and practical activities were informed by a philosophical mind that sought in all circumstances the most general underlying principles; by a juridical mind that sought to bring order and structure to human interaction, without sacrificing the necessary flexibility; by an argumentative mind that knows that persuading is often more important than proving; by a scientific mind eager to organize past and present knowledge so as not to miss any bit of information capable of pointing the way to new discoveries; by a theologian mind that refuses to admit that religious conflicts between true believers are irresolvable; and by an ethical and political mind whose major concern is to direct all our intellectual work towards improving the well-being of humankind.