This last type of problem resembles stage 1 of the inductivist scheme, but only superficially. For an unexpected observation never initiates a scientific discovery unless the pre-existing theories already contain the seeds of the problem.

Genes embody knowledge about their niches. Everything of fundamental significance about the phenomenon of life depends on this property, and not on replication per se.

It is only an accident of evolution, as it were, that the senses we are born with are not adapted to feel such things ‘directly’.

If it is adapted, then it has the property that once it is embodied in that niche, it will tend to remain so.

Dr Johnson’s criterion tells us to regard as real those complex entities which, if we did not regard them as real, would complicate our explanations.

We can give a definition of adaptation directly in terms of knowledge: an entity is adapted to its niche if it embodies knowledge that causes the niche to keep that knowledge in existence.

So, which physically impossible environments can be rendered in virtual reality? Precisely those that are not perceptibly different from physically possible environments.

the fact that the multiverse has this property, far from being a minor embarrassment for realism and science, is essential for both – it is the very property that makes science possible. It is not something that ‘we would rather do without’; it is something that we literally could not do without.

The reason why higher-level subjects can be studied at all is that under special circumstances the stupendously complex behaviour of vast numbers of particles resolves itself into a measure of simplicity and comprehensibility. This is called emergence: high-level simplicity ‘emerges’ from low-level complexity.