Sentence:  At this same time Gadamer was at work on his <WSD>habilitation</WSD> with Heidegger. His <WSD>habilitation</WSD>, "Plato's Dialectical Ethics", concerned Plato's understanding of the good, and its two leading concepts were dialogue and dialectic. 
Meaning of the word marked with <WSD> tags:  An academic qualification, prerequiring a PhD, required in order to gain tenure as a professor in some European universities; a thesis or dissertation presented to achieve the qualification.