Gottfried Wilhelm Leibniz (1646-1716) is one of the most important thinkers of the early modern period. He had an original and decisive contribution to the development of various sciences, including mathematics and physics, but he also dealt with historiography, the theory of law, geology, theology, and more. Leibniz was also one of the most important philosophers in the European philosophical tradition. In 1686 he wrote a short essay known as Discourse on Metaphysics. This essay led to a long and extensive correspondence between him and the important French theologian and philosopher Antoine Arnauld (1612-1694). The article and correspondence are considered the formulation of Leibniz's fundamental philosophical concepts. They are also very interesting philosophical documents, and discuss fundamental philosophical questions, such as the question of freedom and necessity, the question of personal identity and more.