Abstract : For thirty years, there has been a real international willingness to standardize accounting standards and to increase security within the banking and financial system. The IASB and the Basel Committee are working together in the same direction, surrounded by controversial issues such as the ‘fair value'. The 2007-2008 financial crisis has intensified the antagonism between the parties. In this thesis, we intend to demonstrate that we lived in a world of paradoxes : the paradox of Goldilocks (Minsky 1992), the paradox of credibility (Borio & Loewe 2002) and the paradox of security. We have become blinded by a cindynique expulsion (Kervern 2008), which has caused much ‘burying of heads in the sand'. We did not want to see the uncominging danger. But the crisis has also given us the opportunity to examine the market efficiency (Fama 1965) in contrast with the behavioural finance (Kahneman & Tversky 1979). Thanks to our new methodological choices we have been able to replace the apprehension of the market and the market itself which has dominated our concerns, by developing contributions and recommendations mainly for the banking community.