The idea of a man from the future presenting himself at your back door seems like a surreal device to explain how transient our lives really are. What if it suddenly occurred to us that we should answer to future generations for our actions? None of us feels connected to their lives in any way. Every puzzle we solve and every time we invent something new changes how we live, and has the potential to recalibrate and reorganise our world. We must accept that we are the future's past and the past's future. None of us has the power to change the whole world, but each of us is directly accountable to those who will follow us.