Using set theory in the first part of his book, and proof theory in the second, Gaisi Takeuti gives us two examples of how mathematical logic can be used to obtain results previously derived in less elegant fashion by other mathematical techniques, especially analysis. In Part One, he applies Scott- Solovays Boolean-valued models of set theory to analysis by means of complete Boolean algebras of projections. In Part Two, he develops classical analysis including complex analysis in Peanos arithmetic, showing that any arithmetical theorem proved in analytic number theory is a theorem in Peanos arithmetic. In doing so, the author applies Gentzens cut elimination theorem.