Abstract
The three hundred and fiftieth birthday of René Descartes and the three hundredth of G. W. Leibniz, both being commemorated this year, recall to mind an epoch which, in many respects, resembled our own more than any other period of modern history. The Thirty Years' War during which Descartes served four years in the armies of the Dukes of Nassau and Bavaria and the aftermath of which determined many circumstances of Leibniz's life and work, was largely an ideological war leaving Europe in a state of tension, which the Peace of Westphalia did little to allay. As a matter of fact, the strife continued in many changing forms up to the time of the American Declaration of Independence and the French Revolution, if it can be said at all to have been terminated by these events