In philosophy the word “realist” denotes people who believe in an objective reality (Dr Johnson). How ironic that Realist tries (in vain) to deny this (“Physics confirms that ‘objective reality’ is a grand illusion”, March 15).
To mention quantum physicist Eugene Wigner in support of his claim doesn’t help. Wigner said an observer is needed for a wave function to collapse to one of its possibilities – a particle. The observer must naturally possess a consciousness to be able to observe the collapse. And doesn’t the collapse show there has to be “something” that collapses?
Wigner died in 1995. Since when many new theories in quantum mechanics (QM) have been developed by the power of intellect (not by feeling!) One big breakthrough was the Decoherence theory: through the billions of interactions between particles the wave function of big objects is “nudged” to collapse by choosing one of the possibilities to become manifest. No conscious observer is needed, and decoherence offers an explanation of why humans see the moon (or any other big object) in the same place. Decoherence builds a bridge between QM and classical physics and solves the Schrodinger Paradox of a cat that can be both alive and dead at the same time. Instead of existing in two states at once, the cat is “nudged” back into the universe of classical physics where there is simply a 50-50 chance of it being alive (or dead).
To say Wigner made a breakthrough is denying history. Plato theorised that what humans perceive is not reality. Meanwhile Kant gives a splendid explanation of how humans construct reality from raw data by using universal categories. These categories explain how subjective reality becomes a shared reality in which we can all live together. This would be impossible if the Realist was correct in his opinion that every individual has its own particular reality.