The original reason for dipping karpas goes back to Greco-Roman times, when it was customary to eat vegetables with dips as appetizers before the meal (and in the original seders, the meal was eaten at the beginning - not the end - thus enabling the children to ask the four questions about what they had just seen, rather than what was to come). Parsley was a palate cleanser. 

Later, various other explanations were offered for karpas (derived from the Greek "Karpos", meaning fruit of the soil), including  that it acknowledged the spring harvest season, encouraged children to ask questions (in places where the custom of pre-dinner dipping was no longer, or was never, a norm), and recalls the abusive labour that our ancestors endured as slaves, since Karpas dipped in salt water resembles the people’s tears.

The dipped appetizer, therefore, went from cultural norm to vestige (just as reclining/leaning did -- see section on Mah Nishtanah!). Because of this, the third of the four Mah Nishtanah questions asks why we dip at all. The answer reflects a philosophy that is based in common practice. We are who we are because we do what we do. Performing the ritual is important not because it is intrinsically rich with meaning; rather, the ritual is rich with meaning because it is what we do. As we travel through time, we carry our tradition’s wisdom and historical memory and layer upon it, bestowing it with contemporary wisdom. This is what keeps it relevant and vibrant.

Commitment to a continuity of ritual practice demands that on an ongoing basis, we pursue and bestow new meaning in our own context. Every generation needs to read itself into the narrative that it has inherited. The Haggadah clearly states, “Bchol dor va’dor . . . . In every generation a person is obligated to envision himself as if he left Egypt.” We need to imagine ourselves into the past; but also, to bring the past into the present.

haggadah Section: Karpas
Source: Adapted from