Abstract
Under mitigation of damage principle, the injured party must act reasonably to reduce damages; the extent of expected care is the act of a reasonable person at the same conditions and circumstances. Breach of such duty does not cause liability, but reduces the amount of recoverable damage. This principle is applicable both in contractual liability and torts. There are various viewpoints about basis of mitigation rule. Authors and courts suggested some opinions in this matter such as, causal link, contributory negligence and foreseeability of damages theory, good faith principle and economic basis. In Islamic law, the rule of Igdam, which is another feature of causal link, is considered as a basis of mitigation of damage principle. This article examines these fundamentals in Iranian and comparative law.