This book examines frugality as an ideal and an 'art de vivre' which implies a low level of material consumption and a simple lifestyle, to open the mind for spiritual goods as inner freedom, social peace and justice or the quest for God or 'ultimate reality'. By rational choice we can develop a more frugal and sufficient way of life, but material temptations can always overwrite our ecological, social and ethical considerations. But the spiritual case for frugality is strong enough. Spiritually based frugal practices may lead to rational outcomes such as reducing ecological destruction, social disintegration and the exploitation of future generations.