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Can octopuses feel pain and pleasure? What about crabs, shrimps, insects or spiders? How do we tell whether a person unresponsive after severe brain injury might be suffering? When does a fetus in the womb start to have conscious experiences? Could there even be rudimentary feelings in miniature models of the human brain, grown from human stem cells? And what about AI?

These are questions about the edge of sentience, and they are subject to enormous, disorienting uncertainty. We desperately want certainty, but it is out of reach. The stakes are immense, and neglecting the risks can have terrible costs. We need to err on the side of caution, yet it's often far from clear what 'erring on the side of caution' should mean in practice. When are we going too far? When are we not doing enough?

The Edge of Sentience presents a comprehensive precautionary framework designed to help us reach ethically sound, evidence-based decisions despite our uncertainty. The book is packed with specific, detailed proposals intended to generate discussion and debate. At no point, however, does it offer any magic tricks to make our uncertainty go away. Uncertainty is with us for the long term. We must manage our uncertainty by taking precautions that are proportionate to the risks. It's time to start debating what those steps should be.

Jonathan Birch, Professor of Philosophy, Centre for Philosophy of Natural and Social Science, London School of Economics and Political Science

Jonathan Birch is a Professor of Philosophy at the LSE and Principal Investigator on the 'Foundations of Animal Sentience' project, a European Union-funded project aiming to develop better methods for studying the feelings of animals and new ways of using the science of animal minds to improve animal welfare policies and laws. In 2021, he led a review for the UK government that shaped the Animal Welfare (Sentience) Act 2022. In 2022-23, he was part of a working group that investigated the question of sentience in AI.

Summary of the framework and proposals1. A walk along the edge2. The concept of sentiencePART I: The Zone of Reasonable Disagreement3. The mind-body problem4. Ethics and religion5. The science of consciousness and emotionPART II: A Precautionary Framework6. Converging on precautions7. Involving the public8. Debating proportionalityPART III: Sentience and the Human Brain9. People with disorders of consciousness10. Foetuses and embryos11. Neural organoidsPART IV: Sentience in Other Animals12. The clearest candidates13. Pushing the boundaries14. Frontiers of proportionalityPART V: Preparing for Artificial Sentience15. Against complacency16. Large language models and the gaming problem17. The run-ahead principleStepping back