Tonight we drink four cups of wine. Why four? Some say the cups represent our matriarchs—Sarah, Rebecca, Rachel, and Leah—whose virtue caused God to liberate us from slavery. Another interpretation is that the cups represent the Four Worlds: physicality, emotions, thought, and essence. Still a third interpretation is that the cups represent the four promises of liberation God makes in the Torah: I will bring you out, I will deliver you, I will redeem you, I will take you to be my people (Exodus 6:6-7.) The four promises, in turn, have been interpreted as four stages on the path of liberation: becoming aware of oppression, opposing oppression, imagining alternatives, and accepting responsibility to act.
haggadah Section: Kadesh
Source: http://velveteenrabbi.com/VRHaggadah.pdf