There are three aspects of Pesach listed by Rabban Gamliel and in order to fulfill the obligation, one must recite all three (Pesach, Matzah and Maror). But why must one read ALL three aspects in order to fully fulfill their obligation at the seder? According to Raban Gamliel, if one recited only two of the three, one would not have fulfilled the mitzvah because each and every one of them is necessary in creating the story of Pesach. The reason we recite the Pesach is because Hashem passed over the houses of our fathers in Egypt. The reason we recite the Matzah is because the dough of our fathers did not have time to become leavened and the reason that we should recite the Maror is because the Egyptians embittered the lives of our fathers in Egypt. Each component depends on the other for the narrative, and indeed, the seder experience, to progress.

haggadah Section: -- Four Children
Source: Original