A monumental event. William MacAskill is one of the most important philosophers alive today, and this is his magnum opus.' Rutger Bregman, author of Humankind 'A book of great daring, clarity, insight and imagination. To be simultaneously so realistic and so optimistic, and always so damned readable... well that is a miracle for which he should be greatly applauded.' Stephen Fry Humanity is in its infancy. Our future could last for millions of years - or it could end tomorrow. Astonishing numbers of people could lead lives of great happiness or unimaginable suffering, or never live at all, depending on what we choose to do today. As we approach a critical juncture in our history, we can make profound moral decisions about how humanity's course plays out. We can create positive change on behalf of future generations, to prevent the use of catastrophic weapons and maintain peace between the world's great powers. We can improve our moral values, navigating the rise of AI and climate change more fairly for generations to come. The challenges we face are enormous. But so is the influence we have. If we choose wisely, our distant descendants will look back on us fondly, knowing we did everything we could to give them a world that is beautiful and just.