Homo Deus: A Brief History of Tomorrow

Harari explores the complexities and mysteries surrounding human consciousness and the idea of a unique human essence or soul. Harari explores whether humans have a distinct quality that elevates them above other animals, particularly in moral terms.

The chapter begins by questioning the basis of human superiority. Harari challenges the assumption that human life inherently holds more value than animal life, questioning whether might makes right in this context. He contrasts the way societies value human lives differently based on geopolitical power, using the example of an American versus an Afghan life, and then extends this discussion to the comparison between humans and animals.

Harari critically examines the traditional monotheist view that humans have eternal souls while animals do not. He highlights how modern scientific discoveries, particularly in neuroscience, contradict this belief. Extensive research shows no evidence of a soul in humans or animals, and this view is further supported by the principles of evolution, which are based on change and adaptation rather than the existence of immutable, eternal entities like souls.

The chapter then tackles the concept of consciousness, emphasizing how little is actually understood about it despite its central role in experiences of emotions and sensations. Harari points out that while scientists can observe and manipulate brain activity correlated with feelings like love or anger, the subjective experience of these emotions remains a mystery.

Another interesting point Harari raises is the idea that consciousness might be a biologically useless by-product, like the roar of a jet engine. He suggests that feelings and sensations might be “mental pollution,” an unintended consequence of brain activity.

Harari also discusses the complexity of proving consciousness in other beings, including animals and, potentially in the future, AI. The Turing Test is presented as a measure for determining whether a being has a mind, but Harari notes that it is more about social conventions than a definitive proof of consciousness.

The chapter further discusses the Cambridge Declaration on Consciousness, a significant scientific statement recognizing that non-human animals, including mammals, birds, and even octopuses, possess neurological substrates that generate consciousness. This shifts the burden of proof to those who argue that animals do not have conscious experiences.

In examining animal consciousness, Harari describes experiments with rats that suggest they experience emotions like hope and despair. These studies are important for developing psychiatric medications for humans, but they also imply that rats have feelings similar to ours, further complicating an understanding of consciousness across species.

Harari examines the argument that, unlike other animals, humans possess self-consciousness, a deeper awareness of self that extends across time. He questions whether language is a prerequisite for such self-awareness, citing examples of animals like parrots and scrub jays that show evidence of remembering past events and planning for the future. Harari illustrates this with the story of Santino, a chimpanzee who collected stones to throw at zoo visitors later, hinting at complex planning and possibly a level of self-awareness.

The chapter moves on to the unique human ability for large-scale cooperation, which Harari argues is the real reason for humans’ dominance over the planet. While animals like ants and bees exhibit sophisticated cooperation, it lacks the flexibility found in human societies. Human cooperation is unique because it is not limited to small, intimate groups and does not rely solely on personal acquaintances. This capability allows humans to form large, organized societies and achieve feats like space exploration.

Harari emphasizes that the key to human cooperation is humans’ belief in shared myths and stories, such as religions, ideologies, and economic systems. These shared beliefs, which exist only in the collective imagination, enable people to work together in large numbers and create complex societies.

The narrative then details the role of intersubjective realities—concepts and entities that exist because people collectively believe in them, like money, nations, and religious entities. These intersubjective realities shape humans’ world more powerfully than objective or subjective realities because they’re shared by large groups of people.

Harari further explains that while the life sciences can describe the physical and neurological basis of human actions, they cannot fully explain the power of shared beliefs and narratives that govern human societies. He uses historical examples to illustrate how these shared stories have shaped human history and continue to do so.

The chapter concludes by suggesting that in the future, as technology advances, the boundary between objective reality and the intersubjective myths that drive human societies might blur even further. Harari posits that understanding human history and their future requires people to recognize the power of these shared stories, as they are likely to continue being the most influential forces shaping the human world.