Professor Halfwassen was known especially for his work on Plato and neo-Platonism.
Prior to his position at Heidelberg, he held appointments at Ludwig Maximilians University in Munich and the University of Cologne, where he earned his doctorate.
Halfwassen is the author of Der Aufstieg zum Einen. Untersuchungen zu Platon und Plotin, Geist und Selbstbewußtsein. Studien zu Plotin und Numenios, and Hegel und der spätantike Neuplatonismus, among other works.
(via Sebastian Luft)