As the next part of the cycle 'Library of Co-operative Thought' the article by Wladyslaw Jenner (1885-1957), the co-operative activist at the time of partition of Poland and twenty years of Polish independence between the world wars, is reminded. He was a member of State Co-operative Council, an officer at Ministry of Treasury but also an active economic journalist, the author of books on law and economy and lecturer at the both Jan Kazimierz University and Technical University in Lvov. His article 'Moral Base in Co-operative Activity' was first published in the Bulletins of Co-operative Scientific Institute in 1930. The author analyses human cultural behaviour as a result of extreme but intertwined tendencies to individualism and social behaviour. According to Jenner the egoism is not contributing to the progress. It is the social tendency that is the source of culture and civilisation growth. The history of civilisation is the history of lack of balance between those tendencies. From that perspective Jenner describes historic periods (ancient times, Christianity, modern times) giving short characteristics of liberalism, materialism, enlightenment and communism. According to Jenner, the ideas of co-operative society are a chance to reconstruct the former social balance and to revive the ideas of brotherhood, solidarity and justice.