The historical development of bank liquidity doctrines is surveyed from the real bills doctrine and its antecedents to the present day. The underlying ideas of the succession of several dominant liquidity doctrines are analysed and compared, with attention to their historical contexts and respective weaknesses as exposed by experience. While the real bills doctrine is obsolete as such, its central idea that the liquidity of banks requires their credit to be linked to real income generation in the economy is unique among the different liquidity doctrines and can be useful as the liquidity regulation of banks is now subject to renewed interest.