Born in Antwerp, Geulincx studied and taught at Louvain, until in 1658 he was deprived of his chair. Leaving Louvain he settled at Leiden, where he became a Calvinist. He is principally remembered for his occasionalism, or denial of a causal relationship between mind and body, and for using the image of two synchronous clocks, later made famous by Leibniz, to illustrate his doctrine (see pre-established harmony). But Geulincx requires the constant intervention of God, whereas for Leibniz the harmony is the outcome of the pre-established nature of the related substances. Geulincx also wrote extensively on ethics.