Love endures only when the lovers love many things together and not merely each other.

The remark argues that durable love depends on a shared orientation toward the world rather than an exclusive fixation on the partner. When two people “love many things together”—projects, friends, ideas, places, causes—the relationship gains breadth, resilience, and a continuing supply of meaning beyond romantic intensity. By contrast, loving “merely each other” can become self-enclosed: it risks boredom, dependency, or pressure to make the relationship satisfy every need. The line reflects a modern, companionate ideal of marriage and partnership in which mutual interests and common life-building—rather than pure passion—sustain affection over time.