Something very powerful and elemental is unleashed, just in terms of mental or psychic energy. Somehow the mind opens up. A heightened sensibility/susceptibility.
Events seemed drenched with significance, synchronous, mythic, archetypal.
Whatever terminology is used to explain them, Simon undergoes a change of perception which is beyond his control.
Explainer: Hypomania and Psychosis
This clip is from a 21 minute film that explains the background to the novel, produced by Christina Wheeler and commissioned by John Miles. View the film here in full.