From 1977 lecture by Rav Soloveitchik, transcribed by R. David Etengoff:
"The Rav was fond of the analytical and conceptual distinction between a nisa(object) and a nosa (subject). The former is something or someone acted upon, whereas the latter is an actor in the historical drama we call life. At first blush, we look at Pesach, Matzah, and Maror as mere objects that must be consumed during the Seder (i.e. inclusive of the Korban Pesach when the Holy Temple is extant). Yet, in a creative tour de force, Rav Soloveitchik perceived each of these items as a nosa, as an active participant in the mitzvah of Sippur Yitziat Mitzraim:
Sippur Yitziat Mitzraim is a blend of storytelling, Torah teaching, and eating symbolic food items. It is a fusion of the spoken word and the physiological functions of eating and drinking, the intermingling of physical pleasure with Torah debate, the combining of the word of G-d with an activity motivated by biological pressure and characteristic not only of man but of animals. Eating the paschal sacrifice, mazzah and maror constitutes a double mizvah. The mizvat akhilah, physically consuming these items, is per se, a religious performance, a maaseh kiyum mizvah. But eating the Pesach, mazzah, and maror is also the instrument or medium of Sippur Yitziat Mitzraim, telling the story of the Exodus. We narrate the story not only through speech but through eating as well. [Therefore,] in order to fulfill the mizvah of sippur in the most perfect manner, one must interpret and explicate the symbolic meaning of Pesach, mazzah, and maror."