Light And Matter Are Both Single

In Physics and Philosophy (1958), Heisenberg repeatedly returns to the problem that classical language — built on everyday objects — fails when applied to quantum entities. Electrons behave as waves in some experiments and as particles in others; neither description is complete, and applying both simultaneously leads to contradiction. This passage argues that the apparent wave-particle duality is not a property of light or matter themselves, but an artifact of the categories our language forces on us. Niels Bohr's complementarity principle — which Heisenberg closely followed — held that wave and particle descriptions are mutually exclusive but equally necessary, each capturing one aspect of a deeper reality.