If we would build on a sure foundation in friendship, we must love friends for their sake rather than for our own.

The remark frames friendship as an ethical practice rather than a transaction. By contrasting loving friends “for their sake” with loving them “for our own,” it distinguishes genuine regard—attention to the friend’s intrinsic worth and well-being—from instrumental attachment based on benefit, status, or emotional convenience. The metaphor of a “sure foundation” suggests durability: relationships grounded in self-interest are unstable because they depend on changing needs, whereas disinterested affection can endure disappointment, distance, or shifting circumstances. The sentiment also implies a discipline of self-scrutiny, urging the speaker to examine motives and to treat friendship as a form of moral integrity.