Encouraging someone to talk about themselves produces more goodwill than any argument the listener could have made.
Carnegie's point is partly about scarcity and partly about the mechanics of persuasion: a person who has been heard is more willing to hear, and a person who has explained their position has often located its weaknesses without assistance. The technique costs nothing and is rare enough to be conspicuous.
In practice
- A complaint handled by letting the complainant finish resolves at a lower level than one answered immediately.
- A negotiator who asks and waits learns the other side's constraint, which was the thing worth knowing.