 A second challenge draws attention to the fact that many emitters are no longer alive. Why, the objection goes, should those alive now foot the bill for the acts of previous generations? Again responses have been forthcoming. Some may adopt a collectivist approach and hold that the relevant agents are collective bodies like states, and so they hold that since country X emitted in the past country X should pay now. Some, by contrast, respond by appealing again to the idea of benefiting. They hold that individuals alive today (and in the future) enjoy benefits that result from previous emissions-generating activities and so have a duty to pay at least some of the costs incurred in their production. (For discussion see Neumayer [2000: 189], Shue [2014: 186] and Gosseries [2004: 41–55].)