Which 1943 book did C.S. Lewis write about the dangers of rejecting objective moral values?

C.S. Lewis wrote The Abolition of Man about the dangers of rejecting objective moral values.

The Abolition of Man was published in 1943 and developed from three lectures Lewis delivered at Durham University in February of that year. The book examines education, moral judgment, and the idea that some values are genuinely objective rather than merely expressions of personal preference.

Lewis uses the term “the Tao” for a cross-cultural body of basic moral principles. He argues that attempts to reduce all value judgments to emotion or conditioning can weaken the very standards needed to guide human action. The book’s argument is philosophical rather than a retelling of Christian doctrine, although it is strongly connected to Lewis’s broader religious thinking.

The title can be misunderstood as a prediction about ordinary technological progress. Lewis was instead warning about the possible transformation or loss of human nature if people tried to control humanity while denying any objective moral order.