What We Owe the Future by William MacAskill review – a thrilling prescription for humanity

Tony Soprano told his therapist at his first session that he felt like he came in at the end. Our mental image of our species' future tends to be hazy in the event of an extinction, as hundreds of thousands of years of human activity stretch back behind us.

There is more to see. 99.5% of all human experience has yet to be lived, even if the world population were to fall by 90% and the average mammal was to die off. If we can dodge the catastrophe, then a huge amount of time on Earth is still to come.

We are the ancients according to William MacAskill. In the most distant past, we live at the start of history. It can seem like leaving the planet for a few stragglers left to come is our moral responsibility when we think about it. It is possible to influence the fate of almost all the humans there.

Unapologetically optimistic and bracingly realistic, this is the most inspiring book on ‘ethical living’ I’ve ever read

A book called What We Owe the Future: a worthy but depressing reminder that the world is heading to hell in a handcart, informs you it's your duty to live a life of self, is a startling reflection. You wouldn't be right. MacAskill believes that longtermism is a key moral priority of our time. This is by far the most inspiring book on ethical living I have ever read. It made me change the amount and targets of my donations immediately. Longtermism is more exciting than wallowing in anguish about the future in order to reinforce the idea that it is morally good.

The first big surprise is that What We Owe the Future isn't just about the climate. MacAskill is cautiously optimistic, pointing to the rising cost of renewable energy and other positive trends. It is also because of more neglected threats. One of the reasons we lose control of innovations in artificial intelligence is that we lose control of the machines themselves once they become better than humans. Without urgent collective action now, we might share the fate of Chimpanzees or ants vis-a-vis humans: ignored at best and with no say over the future of civilization. There is a weapon that could kill a lot of people. According to MacAskill, experts typically put the chance of an extinction-level engineered pandemic this century at around 1%.

MacAskill believes that it isn't just a question of making the best of a bad job, but of doing what we can to ensure that life for our successors isn't terrible. We have the chance to make a lot of people happy. He argues that it is our responsibility to prevent the existence of a happy and flourishing life. It would be better for an extra human to come into being if they are happy. The moral force of longtermism is that we should save the climate, control artificial intelligence and stop the spread of diseases because the end of humanity would mean trillions of unhappy lives. Those lives could be great. Even for kings or queens in the past, the best quality of life would have been impossible.

We should want the world's population to grow, so that more and more lives can flourish, and we should see having children as a way to do that. The environmental argument against parenthood rests on a pessimistic assumption about the role your children might play in creating a better world. It doesn't take into account the potential human happiness you're taking from the future - your children's happiness, and those of their children, and their children's children.

Is it possible to help the future billions besides having kids? MacAskill is certain that we are uniquely placed to do that because we live in an era of rapid change that can't last long. We would need to extract trillions of times the world's current economic output from each atom to continue economic growth. We have more power to affect the future than those who will inherit it. There are many specific and achievable things governments and corporations need to do, and that we need to pressure them to do through activism and voting.

Giving $3,000 to the right clean energy charity will make more difference to the climate than a lifetime of not eating meat

It is important to focus on moral lock-in because the norms we establish now are likely to persist for a long time. MacAskill believes that there was nothing inevitable about the end of slavery. Ownership of others was not a given. Society allowed an eccentric band of Quakers to nurture their ideas until they caught on. The moral advance came not from society's leaders pursuing the values they were confident were correct, but from a climate in which multiple and often marginal views could thrive.

MacAskill is a co- founder of the "effective altruism" movement and is passionate about targeted financial contributions. He considers the focus on personal ethical lifestyle changes to be a major strategic blunder, since it is good to be a vegetarian, but not good to not eat meat for the rest of your life. Cash donations to causes more neglected than the climate can make even more money because the marginal value of your contribution is bigger. The book promises a life that is less burdened by ethical guilt and more effective at helping humanity, by beating yourself up over every choice of grocery or transportation. It's a life you enjoy so much that you want the same for billions more humans to come.