Feb 25, 2025 “The Moral Circle: Who Matters, What Matters, and Why” by Jeff Sebo (2025, WW Norton)
A new book by philosopher Jeff Sebo presents a series of arguments for expanding the group of entities regarded as moral patients to include all conscious beings. Sebo contends that consciousness is the key factor distinguishing which entities should be included in a broader moral circle and which can be excluded. He argues that consciousness is necessary for any entity to be considered sentient, meaning it can have positive or negative experiences. Recently, Sebo was involved in producing a statement that animals are conscious, which has been signed by hundreds of academics.
The book highlights that while philosophers often disagree, they have more consensus than might be evident from ongoing debates in philosophical literature. For instance, most philosophers agree that all vertebrates are conscious. However, Key makes a notable counterargument, claiming that fish are not sentient, a conclusion disputed by many of the related commentaries on the topic. Conversely, there is much less agreement regarding the sentience of invertebrates, as discussed by Crump et al. (2022), and very few individuals agreee that plants possess sentience, a position argued by Segundo-Ortin & Calvo (2023).
Sebo introduces a thought experiment involving a reader who shares an apartment with two roommates. While both appear to be Homo sapiens, one is Homo neanderthalensis, and the other is a humanoid robot whose brain is composed of silicon chips. In both instances, the behavior and appearance of the two roommates are indistinguishable from that of humans.
Sebo expands on the thought experiment by arguing that humans should widen the moral circle to include beings with a non-negligible chance of possessing consciousness. According to Sebo, this non-negligible criterion is roughly defined as a one-in-a-thousand chance. In his book, The Edge of Sentience, Birch also emphasizes the negative consequences of denying sentience to human neonates, other animal species, or artificial intelligence systems when they are, in fact, sentient. Both Sebo and Birch believe it is better to assume a being is sentient (even if it might not be) than to incorrectly assume that a being is insentient.
Sebo admits that his argument may lead to what the philosopher Derek Parfit referred to as the “repugnant conclusion.” This conclusion suggests that a large population of beings, each leading lives barely worth living, could be considered preferable to allowing a relatively small population of beings with a high quality of life to continue existing. Parfit rejected the Repugnant Conclusion as unacceptable, and many philosophers share this view. However, finding a moral theory that avoids the Repugnant Conclusion has proven surprisingly tricky without leading to equally counterintuitive outcomes.
Sebo acknowledges that he finds the implications of his arguments concerning. I believe that most readers of this relatively short book (192 pages) will share similar feelings about his conclusions. However, being challenged often leads to positive outcomes. At the very least, reading the book should reinforce the reader’s awareness of their consciousness!