Abstract
The concept of moral hazard is increasingly used by insurers to obtain the nullity ab initio of the insurance contract in case of concealment or non-disclosure of facts by the insured. However, the use of this concept is useless when the facts are relevant to the risk covered by the insurance contract. This is because courts use more objective criteria than the simple morality of the insured when it comes time to judge the materiality. Moreover, it appears that this concept is ill-suited to civil law and that litigations can be solved more efficiently by using civilian institutions that protect equally the interests of the insurer.