In Marxism and the Open Mind, John Lewis seeks to explain Marxism as a system of thought. In doing so, he addresses the studied neglect or grotesque misrepresentation that he feels characterizes Western attitudes toward Marxism. Lewis also aims to stimulate what he believes to be a long overdue re-evaluation of Marxism in the light of what was contemporary thought in 1957, the year of the book's original publication and the height of the Cold War era.

The essays include chapters on human rights and a discussion on Marxism and liberty. Marxist ethics, a much-neglected theme, is the subject of an essay that deals with some of the most deeply felt criticisms of Marxism in the 1950s. The ethical aspects of Marxism are examined once again in a contribution to the debate on Marxism and religion. The volume concludes with essays on Berdyaev and Sartre, which strike a note on the Marxist estimation of these thinkers, and with an essay on Marxist humanism.

The essays cover a wide field of thought, uniting a close and sympathetic study of Marxism with a critical judgment rooted in academic training at three universities and experience in the Christian ministry.