 According to both  Cart  and  Eells,  a cause must raise the probability of its effect in every background context. This has been called the requirement of contextual-unanimity. Dupré (1984) raises the following counterexample to the contextual unanimity requirement. Suppose that there is a very rare gene that has the following effect: those that possess the gene have their chances of contracting lung cancer lowered when they smoke. In this scenario, there would be a background context in which smoking lowers the probability of lung cancer: thus smoking would not be a cause of lung cancer according to the contextual-unanimity requirement. Nonetheless, it seems unlikely that the discovery of such a gene would lead us to abandon the claim that smoking causes lung cancer. 