The key ideas

Brief Answers to the Big Questions

Stephen Hawking, 2018

Is there a God? Are we alone in the universe? Will we survive on Earth, and will artificial intelligence outsmart us? Stephen Hawking's last book came out after his death and answers ten questions he was asked all his life. Here are his answers as a scientist and as a person, with an honest line drawn between physics and forecast.

Who it is for

For anyone who wants to know what the great physicist thought about God, aliens, AI and the human future, and where the science ends and his personal opinion begins.

Remember to look up at the stars and not down at your feet.

What the book is about

At 21, Stephen Hawking was diagnosed with amyotrophic lateral sclerosis. The doctors gave him about two years. He lived for more than half a century after that.

This book came out in October 2018, a few months after his death. It was put together from his essays and lectures. It holds ten questions he was asked all his life: Is there a God? Are we alone? Can we travel into the past? Will we survive? Will artificial intelligence outsmart us?

People usually take questions like these to priests, philosophers or science fiction writers. Hawking answers as a physicist: through the laws of nature. Then he asks: what does this mean for us?

Every answer follows the same rhythm: the question, the scientist's answer, what follows from it. Along the way we'll mark where physics is speaking and where it is Hawking's personal opinion and forecast.

Idea 1. Is there a God? Laws instead of a conductor

The first question, and the sharpest. Hawking's answer is blunt: “There is no God. No one directs the universe.”

How does he get there? The laws of nature, as he sees it, work without exception, which leaves no room for anyone to step in from outside. And to the question “who set off the Big Bang?” Hawking has a physical answer: in his model, time itself began together with the universe. If there was no “before”, there was no moment when anyone could have created it. The universe, Hawking believes, could have arisen on its own, by the laws of physics.

He adds a caveat: everyone is free to believe what they like, and for him the simplest explanation is that there is no God. He did not believe in an afterlife either.

What does this mean for us? If no one directs the universe, no one will fix our mistakes for us.

The laws of nature are the foundation of science, but the conclusion “there is no God” is Hawking's philosophical position. Physics can neither prove nor disprove the existence of God, and many scientists and philosophers disagree with him.

Hawking compared the question “what came before the Big Bang?” to asking “what lies south of the South Pole?” The words are in the right order and a direction is named, but the place you are asking about simply does not exist.

If the world runs on laws rather than on someone's will, responsibility for the future passes to the people who understand those laws and use them.

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About the author

Stephen Hawking (1942–2018) was a British theoretical physicist, a professor at the University of Cambridge and the author of A Brief History of Time. He is known for his work on black holes and the origin of the universe. He lived most of his life with amyotrophic lateral sclerosis.

All books by this author: Stephen Hawking

Terms from the book

  • Space-time
  • DNA
  • greenhouse effect
  • Laws of nature
  • Cambridge
  • Artificial intelligence
  • Big Bang
  • General relativity
  • Alpha Centauri
  • Milner
  • Breakthrough Starshot
  • Amyotrophic lateral sclerosis: A severe, incurable disease of the nervous system: the muscles gradually stop working. Hawking lived with it for more than half a century, though people usually live only a few years after the diagnosis.
  • External transmission of information: An image from the book: knowledge builds up not only in genes but in language, books and computers. That is why humanity changes faster than its DNA.
  • Probe: An uncrewed spacecraft sent out to explore space.
  • Light sail: A very thin sail pushed by the pressure of light, for example a laser beam. Breakthrough Starshot is built on it. For now it is a plan, not a finished technology.
  • Superintelligent AI: A hypothetical artificial intelligence that outdoes humans at almost everything. It does not exist yet; Hawking speaks of its risks as a forecast.
  • Gene editing: Technologies that make precise changes to the DNA of a living organism, such as fixing or replacing individual stretches of genes.
  • Self-designed evolution: Hawking's idea of a future in which people change their own genes. It is his forecast, not a description of something already happening.

All terms

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