  We provide a conceptual discussion and physical interpretation of some of the
quite abstract constructions in the topos approach to physics. In particular,
the daseinisation process for projection operators and for self-adjoint
operators is motivated and explained from a physical point of view.
Daseinisation provides the bridge between the standard Hilbert space formalism
of quantum theory and the new topos-based approach to quantum theory. As an
illustration, we will show all constructions explicitly for a three-dimensional
Hilbert space and the spin-z operator of a spin-1 particle. This article is a
companion to the article by Isham in the same volume.
