Question

First of all, many thanks for the lessons on Talmudic-analytical thinking. Fascinating, delightful, and clear ideas—as if given at Sinai itself. Fortunate are you, and fortunate is she who bore you, that you merited to illuminate the Torah in this way. 
You mentioned at the beginning of the lesson another lesson by a rabbi (whose name I couldn’t make out on the recording) about three legal categories in the language of betrothal. Which rabbi was this, and could you point me to that lesson (assuming it was documented)? 
All the best