In Then I Am Myself the World, Christof Koch explores the only thing we directly experience: consciousness. At the book's heart is integrated-information theory, the idea that the essence of consciousness is the ability to exert causal power over itself, to be an agent of change. Koch investigates the physical origins of consciousness in the brain and how this knowledge can be used to measure consciousness in natural and artificial systems. Enabled by such tools, Koch reveals when and where consciousness exists, and uses that knowledge to confront major social and scientific questions: When does a foetus first become self-aware? Can psychedelic and mystical experiences transform lives? What happens to consciousness in near-death experiences? Why will generative AI ultimately be able to do the very thing we can do, yet never feel any of it? And do our experiences reveal a single, objective reality? This is an essential book for anyone who seeks to understand ourselves and the future we are creating.