Causation (or causal link) is considered as a basic element and an essential condition of the civil liability arising from the tort in general, and the tort of negligence, in particular. In the law of torts, which is a part of the English Common law of customary origins, which is unwritten and based upon judicial precedents of the English courts. It is worth-bearing in mind that the causation is a causal link by which the damage suffered by the plaintiff arises from the defendant's breach of duty of care. And this link is proved in the English law by many criteria, the most important of which are the factual causation criterion, or the ‘but for’ test. The direct causation criterion, or the remoteness of damage test. The all or nothing criterion, and The Material Increase in Risk criterion. Whereas the Iraqi civil law No. (40) of 1951 regulated also the causal link and considered it as an independent element of the civil liability, whether it be contractual or tortuous. And put the burden of its proof originally on the plaintiff, according to the general rules of evidence. But it put the onus of proving exceptionally on the defendant within the scope of the vicarious liability, in which an irrebuttable presumption arises against the guardian and the employee.