© 2017 Social Philosophy & Policy Foundation. Printed in the USA. Liberal thinkers of the Enlightenment understood that surplus moral constraints, imposed by invalid moral norms, are a serious limitation on liberty. They also recognized that overcoming surplus moral constraints - what we call proper demoralization - is an important dimension of moral progress. Contemporary philosophical theorists of liberty have largely neglected the threat that surplus moral constraints pose to liberty and the importance of proper de-moralization for human emancipation. This essay examines the phenomena of surplus moral constraints and proper de-moralization, utilizing insights from biological and cultural evolutionary thinking.