Johannes Jacobus Poortman (April 26, 1896 in Rotterdam – December 21, 1970 in The Hague), studied philosophy and psychology at Groningen University under Professor Gerardus Heymans.
Poortman studied at the universities of Hamburg, Geneva, the Sorbonne in Paris and at Vienna.
After he retired his chair was successively occupied by Prof. Dubbink, Prof. van Vledder and Prof. Gerding.
Poortman was the maker of the Repertory of Dutch philosophers, Repertorium der Nederlandse Wijsbegeerte, which can be consulted on line at the site of the Leiden University.
Poortman distinguished six different metaphysical views of the world, which he named from Alpha to Zeta.