The Matter With Things: Our Brains, Our Delusions and the Unmaking of the World

by Iain McGilchrist

Newtonian mechanics is at one level incompatible with quantum mechanics. It does useful work at the level of day-to-day reality, but at the subatomic level, or at the cosmological level, it no longer applies. But it is not that quantum mechanics applies only at the extremes of magnitude, and Newtonian mechanics, which contradicts it, applies only in the bit in the middle where we normally focus. That would be like saying the earth is curved elsewhere, but flat wherever we happen to be. It’s always curved: just for everyday purposes it looks flat, and we don’t need to take the curve into account. Similarly, quantum mechanics applies across the whole field; Newtonian mechanics is just a handy approximation that can be overlaid on quantum mechanics for practical purposes, provided it is restricted to the day-to-day level. It won’t help us understand the underlying reality – in fact it misleads us there. But it has its own, prodigious, usefulness. Note that it is the precision of Newtonian mechanics that makes it a less good fit, while the intrinsically less precise quantum mechanics is more accurate.