243 Essays on Infinite Lifespans   Marc Geddes then B’s angry friends could strike back. Be nasty to people and they are more likely to be nasty back. Tit for Tat. From Hobbes and Locke came the idea of a ‘Social Contract’. [1] A contract is a formal or informal agreement whereby parties agree to recognize various obligations to one another. In the case of the ‘social contract’ the idea is that everyone living in a society has implicitly agreed to play by a set of rules because, over  the  long  run,  playing  nice  makes  everyone  better  off than  they  would  be  in  the  anarchistic  ‘Hobbesian’  world. These ideas form the basis of a political philosophy known as ‘Contractualism’. Rational people understand that actions have consequences. A life of crime may help a person in the short term, but in the long run it may get you killed or imprisoned. That we recog- nize it is in our own long-term interests to respect others leads to moral behavior. When we respect the rights of other people, they are more likely to co-operate with us, to mutual benefit. Of course, for this to work people have to learn to defer short- term gain in favor of long-term benefit. The critical point is a person’s awareness that they have a future. People are more likely to be moral when they understand they will have to face the consequences of their actions in the future. It follows that the further into the future one plans for, the more moral one’s behavior should become. People that live a short time do not have to experience the future consequences of all their actions. Longer lives should reduce the tension between the individual and society. The extent to which moral behavior stems from the ability to plan for the future has perhaps not been properly recognized as  of  yet.  Evolutionary  biologists  have  tried  to  understand moral behavior such as altruism in terms of the possible sur- vival advantages it would bring. But moral behavior cannot be fully explained in this way – if we only consider the short- term.