Keynes initially saw banks as middlemen between savers and borrowers, but later focused on people's desire for cash and balance in the economy. In 1937, he reintroduced banks with the 'finance motive', but his views didn't change much. Ohlin and Robertson disagreed with Keynes on interest rates, suggesting that they are determined by credit supply and demand. Keynes also discussed how financial markets are influenced by conventions and speculation, a key aspect often overlooked by many.