Studies in the history of philosophy often analyze philosophers’ views in relation to the stage of the exact sciences of their times. While this is common practice in general, for some reason it has never been undertaken for Edmund Husserl (1859–1938), who nevertheless was originally a mathematician.1 One likely reason for this neglect is a tendency to downplay the role of the exact sciences in Husserl’s philosophical views and their development. Yet, discussion of the foundations of these sciences has a central role in all of his published monographs.2 In this book, I will show this by focusing on Logical Investigations (1900–1901), Ideas Pertaining to a Pure Phenomenology and to a Phenomenological Philosophy I (1913), Formal and Transcendental Logic (1929), and The Crisis of European Sciences and Transcendental Phenomenology (1936; only parts of this work were published during Husserl’s lifetime).