Which C.S. Lewis book presents the argument that modern society has lost objective values?

The C.S. Lewis book arguing that modern society has lost objective values is The Abolition of Man.

The Abolition of Man began as a series of three lectures delivered at Durham University in 1943. Lewis criticized educational approaches that treated moral judgments as merely subjective feelings and defended the existence of objective values.

The book develops its argument through discussions of education, morality, reason, and the possibility that technological power could reshape or diminish human nature. Its final chapter considers what Lewis called the conquest of nature by man and the consequences of that ambition.

The title is sometimes mistaken for the name of a fictional work, but the book is a compact philosophical and educational critique. It is also distinct from Mere Christianity, which grew from wartime radio talks.