Arnold Geulincx

Arnold Geulincx (January 31, 1624 – November 1669), who wrote under the pseudonym Philaretus, was a Flemish philosopher and logician. He served as professor at the University of Leuven, Belgium for 12 years, and later as professor at the University of Leiden, the Netherlands. Geulincx wrote all his works in Latin, and died before his principal books, namely Ethica and Metaphysica could be published. He summarized his philosophy in the phrase, "Ita est, ergo ita sit", ("it exists, therefore it is so").

He believed in a "pre-established harmony" as a solution to the mind-body problem, dying 25 years before Leibniz's better remembered formulation of the idea.

In Leibniz' philosophy, the doctrine of pre-established harmony was linked with optimism, the notion of this world as the "best of all possible worlds". But Geulincx made no such linkage.