How do banks operate and where does the money supply come from? The financial crisis has heightened awareness that these questions have been unduly neglected by many researchers. During the past century, three different theories of banking were dominant at different times: (1) The currently prevalent financial intermediation theory of banking says that banks collect deposits and then lend these out, just like other non-bank financial intermediaries. (2) The older fractional reserve theory of banking says that each individual bank is a financial intermediary without the power to create money, but the banking system collectively is able to create money through the process of ‘multiple deposit expansion’ (the ‘money multiplier’). (3) The credit creation theory of banking, predominant a century ago, does not consider banks as financial intermediaries that gather deposits to lend out, but instead argues that each individual bank creates credit and money newly when granting a bank loan. The theories differ in their accounting treatment of bank lending as well as in their policy implications. Since according to the dominant financial intermediation theory banks are virtually identical with other non-bank financial intermediaries, they are not usually included in the economic models used in economics or by central bankers. Moreover, the theory of banks as intermediaries provides the rationale for capital adequacy-based bank regulation. Should this theory not be correct, currently prevailing economics modelling and policy-making would be without empirical foundation. Despite the importance of this question, so far only one empirical test of the three theories has been reported in learned journals. This paper presents a second empirical test, using an alternative methodology, which allows control for all other factors. The financial intermediation and the fractional reserve theories of banking are rejected by the evidence. This finding throws doubt on the rationale for regulating bank capital adequacy to avoid banking crises, as the case study of Credit Suisse during the crisis illustrates. The finding indicates that advice to encourage developing countries to borrow from abroad is misguided. The question is considered why the economics profession has failed over most of the past century to make any progress concerning knowledge of the monetary system, and why it instead moved ever further away from the truth as already recognised by the credit creation theory well over a century ago. The role of conflicts of interest and interested parties in shaping the current bank-free academic consensus is discussed. A number of avenues for needed further research are indicated.