1 Introduction

The principal assertion of the spectral theorem is that every bounded normal operator \(T\) on a Hilbert space induces (in a canonical way) a resolution \(E\) of the identity on the Borel subsets of its spectrum \(\sigma (T)\) and that \(T\) can be reconstructed from \(E\) by an integral. A large part of the theory of normal operators depends on this fact.