1. Core Legal Answer & Context: Causation is a fundamental element in tort law, requiring a causal link between the defendant's breach of duty and the plaintiff's damage. When events causing damage are not simultaneous but successive, establishing causation becomes complex. This complexity arises because multiple factors, potentially from different sources or at different times, might contribute to the final harm, making it difficult to isolate the specific impact of the defendant's breach. The traditional 'but for' test (i.e., 'but for' the defendant's act, would the damage have occurred?) often proves inadequate in such scenarios.

In cases of successive causes, courts often grapple with:

• Multiple Sufficient Causes: Where two or more independent acts, each sufficient to cause the entire damage, occur successively.
• Material Contribution: Where the defendant's act, while not the sole cause, materially contributed to the damage, especially when scientific uncertainty makes it impossible to prove the 'but for' link.
• Novus Actus Interveniens: An intervening act that breaks the chain of causation from the defendant's original breach.

2. Relevant Statutes and Sections: Tort law in India is largely uncodified, relying on common law principles developed through judicial precedents. Therefore, there are no specific statutes or sections directly addressing this issue in India, but the principles are derived from English common law and adapted by Indian courts.

3. Important Landmark Cases:

• Barnett v Chelsea & Kensington Hospital Management Committee (1969) (English): This case established the 'but for' test. A patient died after being sent home from a hospital without examination. The court found the hospital negligent but held that even if he had been examined, he would have died anyway. Thus, the hospital's negligence was not the 'but for' cause of death. This shows the limitation of the 'but for' test when the defendant's act is not the necessary condition for the harm.
• McGhee v National Coal Board (1973) (English): This case introduced the concept of 'material increase in risk'. The plaintiff contracted dermatitis from brick dust. The employer was negligent in not providing washing facilities, which increased the risk of dermatitis. While it couldn't be proven that the lack of facilities caused the dermatitis (as some exposure was unavoidable), the House of Lords held that materially increasing the risk of injury was sufficient to establish causation. This is crucial for successive causes where precise attribution is difficult.
• Fairchild v Glenhaven Funeral Services Ltd (2002) (English): This landmark case further developed the 'material contribution to risk' principle. Several employees contracted mesothelioma from asbestos exposure, having worked for multiple employers, each of whom negligently exposed them to asbestos. It was impossible to prove which specific exposure caused the disease. The House of Lords held that each employer who materially increased the risk of the disease could be held jointly and severally liable. This is a prime example of addressing causation in successive, non-simultaneous exposures where the 'but for' test fails.
• Wilsher v Essex Area Health Authority (1988) (English): This case somewhat limited McGhee, reaffirming that a material increase in risk is not always equivalent to material contribution to injury. A premature baby suffered blindness, potentially due to five different causes, one of which was negligent oxygen administration. The court held that merely increasing the risk was not enough; it had to be proven that the negligence caused the injury, distinguishing it from McGhee where all exposures were of the same type.

4. Clear Conclusion: When events causing damage are successive, the ascertainment of causation moves beyond a simple 'but for' test. Courts employ more flexible approaches like 'material contribution to risk' or 'material contribution to injury' to ensure justice, especially in complex scenarios involving multiple tortfeasors or scientific uncertainty. While the 'but for' test remains the primary tool, cases like McGhee and Fairchild demonstrate the judiciary's willingness to adapt causation principles to address the challenges posed by non-simultaneous, successive events in tort law.