The Continuum Problem The Continuum Hypothesis General Continuum Hypothesis Cantor’s Theorem Hartogs’ Lemma Cardinal Independent Sentence Substructure Absolute Transitive Model Formula Hierarchy Definable Operation Absolute Operation Absoluteness Of Recursive Operations Gödel’s Incompleteness Theorems Absoluteness Of Consistency Absoluteness of Truth Lévy Reflection Theorem The Downward Löwenheim-Skolem Theorem Mostowski’s Collapsing Theorem Countable Transitive Model Constructible Model of Set Theory Consistency of Choice Technique of Inner Models Technique of Outer Models