1 Kronecker, the semi-intuitionists, Poincaré.- 1.1 Introduction.- 1.2 Kronecker.- 1.3 The French semi-intuitionists.- 1.4 Poincaré.- 1.5 Conclusion.- 2 The genesis of Brouwer’s intuitionism.- 2.1 Introduction.- 2.2 The early years.- 2.3 The first act of intuitionism.- 2.4 Topology.- 2.5 Intuitionism and formalism.- 2.6 The second act of intuitionism.- 2.7 The Brouwer lectures.- 2.8 The Mathematische Annalen and afterwards.- 2.9 Brouwer’s personality.- 2.10 Conclusion.- 3 Overview of the foundational debate.- 3.1 Introduction.- 3.2 Quantitative inquiry.- 3.3 Qualitative inquiry.- 3.4 Conclusion.- 4 Reactions: existence and constructivity.- 4.1 Introduction.- 4.2 The beginning of the debate.- 4.3 The debate widened.- 4.4 Later reactions.- 4.5 Conclusion.- 5 Reactions: logic and the excluded middle.- 5.1 Introduction.- 5.2 The beginning of the debate.- 5.3 The debate widened.- 5.4 Later reactions.- 5.5 Conclusion.- 6 The foundational crisis in its context.- 6.1 Introduction.- 6.2 Metaphors.- 6.3 Philosophy.- 6.4 Physics.- 6.5 Art.- 6.6 Politics.- 6.7 Moderne and Gegenmoderne.- 6.8 Conclusion.- Conclusion.- A Chronology of the debate.- B Public reactions to Brouwer’s intuitionism.- C Logical notations.- Dankwoord/ Acknowledgements.