For Gödel’s theorems there are truths that escape axiomatic systems. This phenomenon in mathematical logic is called incompleteness. This book deals precisely with mathematical truths that axiomatic systems fail to capture. In the first chapters the incompleteness of Peano’s arithmetic is addressed, Gödel’s sentences cannot be captured by the principles of Peano’s arithmetic. Thus in this book it is possible to see how Gödel was able to construct an arithmetic sentence that says about itself: I am unprovable. In addition to Gödel’s sentences, there are other truths such as Goodstein’s theorem and the finite extension of Ramsey’s theorem which Peano’s axioms fail to prove. In the second part of the book we will see that in modern set theory there is a sentence, namely the Continuum Hypothesis, that Zermelo-Fraenkel axiomatic system fails to prove. For a result of Gödel (1938) and a result of Cohen (1963) the Continuum Hypothesis is independent of the axioms of Zermelo-Fraenkel. These axioms fail to prove the Continuum Hypothesis. In the last part of the book we will see the attempt of Hugh Woodin to prove the Continuum Hypothesis that is called Woodin’s program.