The reason GAAP allows for ethical challenges is because it is a set of recognized "best practices" that do not comprise a rule or professional ethical criteria. As a result, there is room for difference of opinion and perspective. One area that allows for ethical challenges is the principle of conservatism. This holds that business accounting should be "fair" and "reasonable." These terms may be loosely defined or imperfectly defined and understood thus allowing for ethical challenges. Another is the objectivity principle. Objective evidence may be manufactured thus creating a significant ethical challenge.