The Philosophy of Moral Development: Moral Stages and the Idea of Justice

Kohlberg argues that moral development proceeds through a universal, invariant sequence of six stages, each representing a more adequate conception of justice. He rejects cultural relativism—the view that moral judgments are simply expressions of culturally specific values with no rational basis for ranking them. The book defends the strong claim that higher stages are philosophically superior because they are more differentiated, reversible, and universalizable. Justice, not care or virtue, is positioned as the core of moral maturity, and the stages describe formal properties of reasoning rather than specific moral content.

Reversibility is Kohlberg's formal criterion for moral adequacy: a moral judgment is adequate if it can be reversed—that is, if the person making the judgment would accept the same decision if they occupied the position of every affected party. He treats this as the defining feature of Stage 6 reasoning, where principles of justice are applied impartially without privileging one's own perspective. The reversibility criterion allows Kohlberg to claim that Stage 6 is not merely a different moral style but a more advanced form of reasoning, because it alone satisfies the demand for universalizability that he takes to be constitutive of morality.

The six stages are organized into three levels. Preconventional: Stage 1 (punishment and obedience) and Stage 2 (instrumental exchange). Conventional: Stage 3 (interpersonal conformity and 'being good') and Stage 4 (social system and conscience maintenance). Postconventional: Stage 5 (prior rights and social contract) and Stage 6 (universal ethical principles). Kohlberg treats the sequence as invariant—individuals move through the stages in order without skipping—and claims it holds across cultures, though Stage 6 is rarely observed empirically .

Kirkus Reviews described it as a 'magnificent obsession' but noted there is 'really no grand consecutive argument'—the book applies stages to various issues with mixed results, and Kohlberg 'makes enough dogmatic claims to keep an army of critics busy for 50 years' . A theological reviewer observed that Kohlberg's theory was entering a phase of 'severe criticism' in the early 1980s . A philosophical critic catalogued what he saw as glaring inconsistencies, charging that Kohlberg's supposedly formal criteria of adequacy smuggled in substantive liberal-secular-humanist commitments .

A persistent misunderstanding equates higher stages with greater intelligence or better moral behavior. Kohlberg clarifies that stages describe structures of moral reasoning, not IQ or conduct. A person can reason at Stage 5 yet act immorally; the theory predicts judgment, not behavior. The volume also rejects the assumption that Stage 6 represents a specific moral doctrine—such as utilitarianism or Kantianism—insisting instead that it is a formal principle of reversibility. Critics argue, however, that this distinction collapses in practice, since Kohlberg's examples of Stage 6 reasoning consistently endorse egalitarian liberal values .

Kohlberg argues that moral education should aim at stimulating development through the stages, not at indoctrinating children into fixed values. He draws on Dewey and the Socratic tradition to propose that schools create opportunities for moral discussion and democratic governance, particularly through 'just community' approaches. The goal is to provoke cognitive conflict that moves students toward more adequate reasoning. Critics, including some reviewers of this volume, charge that this program is itself a form of value re-education, smuggling in Kohlberg's own conception of justice under the guise of developmental facilitation .