Deep concepts.
Seven concepts that each layer keeps pointing back at: the Hard Problem of Consciousness, Integrated Information Theory, It from Bit, the Holographic Universe, Wolfram's Computational Universe, the Mathematical Universe Hypothesis, the Anthropic Principle.
Named by David Chalmers in 1995, the Hard Problem asks not how the brain produces behavior — that is the easy problem, addressed by neuroscience — but why there is something it is like to have those processes occur. The redness of red, the taste of coffee, the felt quality of grief: every third-person description of the system, no matter how complete, seems to leave the first-person question untouched.
Giulio Tononi's Integrated Information Theory proposes that consciousness is identical to a system's integrated information, denoted Φ — a quantitative measure of how much the system's whole exceeds the sum of its parts in informational integration. The theory is the most mathematically precise current account of consciousness, and it makes specific empirical predictions that have begun to be tested clinically.
John Archibald Wheeler's 1989 lecture proposes the strongest form of the information-substrate hypothesis: every it — every physical entity — derives its existence from bits, from binary answers to questions. The slogan is short but the consequence is large. If true, information is not a useful description of the universe but its substrate.
The holographic principle, conjectured by 't Hooft and Susskind in the 1990s and given a working example by Maldacena's AdS/CFT correspondence in 1997, holds that the full physical content of any region of space is encoded on its boundary. The volume of space we experience is structurally a projection. Information lives one dimension below the geometry.
Stephen Wolfram's project — sketched in A New Kind of Science (2002) and consolidated as the Wolfram Physics Project (2020) — proposes that the universe at its base is a hypergraph whose nodes and edges are continually rewritten according to simple rules. General relativity and quantum mechanics are claimed to emerge as statistical limits of the rewriting process. The project is unproven but its papers have entered serious journals.
Max Tegmark's 2008 proposal makes the strongest possible commitment to mathematical Platonism: not merely that mathematical objects are real, but that every mathematically consistent structure is a universe in the same sense ours is. Our universe is one such structure, and our experience of being "in" it is what one such structure looks like from inside.
First formulated by Brandon Carter in 1973, the anthropic principle observes that any law or constant we can measure is, by construction, compatible with our existence as observers. The principle has a weak form (the universe is necessarily compatible with observers in the region where observers exist) and a strong form (the universe must be such that observers exist somewhere). Each is, in different ways, a partial dissolution of the fine-tuning puzzle.