Each of these senses of responsibility is relevant to issues of product safety and marketing ethics. One of the first, and often most difficult, questions of prod¬uct safety concerns determining the cause of any harms. What caused the Ford Explorers to crash during blowouts of their Firestone tires? Was it the design, the manufacturing process, or some component of the tire? Was it the design and stability of the Explorer? Was it the driver's own behavior? Was it some combination of all these factors? The concept of negligence, a central notion in product liability law, is one way in which fault is assigned (intentionally or reck¬lessly causing harm would be other ways of causing harms). Thus, manufactur¬ers who fail to inspect their products before sending them to the market, or who rush them to market without adequate testing, can be held culpable (at fault) for harms caused by this negligence. The legal doctrine of strict products liability is more a doctrine of no-fault accountability. If a product defect has caused a harm, the manufacturer is held accountable even though not at fault. Finally, some argue that manufacturers should be accountable for the entire life cycle of the products they bring to the market, including recycling the product back into the production stream.