Classical financial theory ignores the existence of financial intermediaries. In neoclassical micro-economics, the capital market brings together agents with financing capacity – investors – and agents with financing needs – companies. Thanks to the private information they possess, the latter on the productive potential of the company, the former on the marginal productivity of their investment, the trade can take place. I propose first of all to review the discourse that legitimises financial intermediaries through economic theory. This naturalised vision of finance could not be further removed from reality: the financial security only exists because of the presence of systems and organisations that give it its attributes (liquidity, status), take care of its distribution (via market institutions, distributors, advisors) and ensure its price history can be traced. The angle adopted is a resolutely micro-economic one, starting with the initial theory of financial intermediation put forward by Gurley and Shaw (1956). In a second part, I will present some socio-politically-inspired approaches that highlight the appearance of financial intermediaries through the possibility of legitimising the capture of economic rents. This aspect, which appears in many recent works focusing on the financialisation of the economy, emphasises the link between financial institutions and certain forms of political domination. Finally, the third part will present some of my own work in the field of social studies of finance which are based on observational field research and which explore the socioeconomic nature of financial intermediation. JEL: G2 Classical financial theory ignores the existence of financial intermediaries. In neoclassical micro-economics, the capital market brings together agents with financing capacity – investors – and agents with financing needs – companies. Thanks to the private information they possess, the latter on the productive potential of the company, the former on the marginal productivity of their investment, the trade can take place. In the Asset Pricing Theory approach, only financial securities are considered, these being defined through two statistical dimensions: their risk and their return. The resulting optimum portfolio depends on these parameters as well as on the investor's degree of risk aversion. Once again, there is no need to seek the services of an intermediary. Naturally, in macroeconomics , we find the same absence. Hicks (1974) contrasts the intermediated economy with the market economy where investors purchase their securities directly from issuers. The bank is distinguished by its inevitable presence in the transformation of deposits into loans. This naturalised vision of finance could not be further removed from reality: the financial security only exists because of the presence of systems and organisations that give it its attributes (liquidity, status), take care of its distribution (via market institutions, distributors, advisors) and ensure its price history can be traced. For financial institutions existed before securities (Carruthers, Stinchcombe, 1999) and it is these institutions and not securities themselves that have driven the development of finance. Without them, without their reputation, without the trust the community places in them, securities