Travelling in France and England, he came to study the Cartesian philosophy under Johannes de Raey at Leiden.

In 1649, he became professor of philosophy and theology at Herborn, but subsequently (1651), in consequence of the jealousy of his colleagues, accepted an invitation to a similar post at Duisburg.

His theory of the connection between the soul and the body is in some respects analogous to that of Malebranche; but he is not therefore to be regarded as a true forerunner of Occasionalism, as he uses Occasion for the stimulus which directly produces a mental phenomenon, without postulating the intervention of God.

The very word "ontology" occurs at least once in an undated fragment of Leibniz,[5] and one can expect accidentally to meet it later in various places, but it is not until 1729 that it finally comes into its own with the Ontologia of Christian Wolff.

A collected edition of his philosophical works was published at Amsterdam (1691), with life by H. C. Hennin; see also E. Zeller, Geschichte der deutschen Philosophie seit Leibnitz (1873).