Collier discusses how moral values often drive reasoning and policy on migration, leading to polarized views and emotional debates, rather than evidence-based decision-making. There is a wide variety in migration policies across nations, including differences in openness, assimilation strategies, and the rights afforded to migrants. These policies are often shaped more by historical legacies and emotional reactions than by careful analysis. Nationalism, according to Collier, fosters cooperation and redistribution within nations but can also breed division and violence. He stresses the importance of disentangling migration discussions from issues of poverty, nationalism, and racism to facilitate rational debate.

Collier approaches the impact of migration through three perspectives: Migrants themselves; the communities they leave behind; and the host countries. Migrants generally achieve substantial economic benefits, though there is some evidence of psychological challenges, such as alienation or loss of identity. For the countries of origin, migration can be a double-edged sword. On one hand, remittances from migrants provide a vital financial lifeline, but on the other hand, emigration often depletes these societies of skilled individuals, leaving them with fewer resources for development.

Collier challenges the simplistic dichotomy of migration being inherently “good” or “bad.