Summary
Agape is love given without regard to whether the person loved has earned it. The word is ancient Greek and took its lasting meaning in the New Testament, where it names God’s love for humans, their love for God and, by extension, love of neighbour and even of enemies. Greek thought sets it beside eros (desire) and philia (friendship).
In Christian teaching it is first of all God’s love, which people receive before they return it; the theologian Anders Nygren called it “spontaneous and unmotivated”. Some later writers have carried the word into non-religious settings, where that grounding in the divine drops away.
Rationale
Early Christians gave the same word to a shared meal, the love feast. That interests us most: a way of relating kept alive through practice, like Part 2’s “ritual, celebration or shared meals”.