The Three Basic Principles

Abstract

AbstractThis chapter is devoted to the so-called three Functional Analysis basic principles: the Hahn-Banach Theorem about continuous extension of linear forms; the Open Mapping Theorem – one of whose consequences has been used in the proof of Theorem 5.1, Sect. 3.2. and the Banach-Steinhaus Theorem, or Uniform Boundedness Principle, which we have also mentioned previously (Theorem 4.2).