In Memoriam: Ulrich Blau (1940–2026)

The Faculty of Philosophy, Philosophy of Science, and the Study of Religion mourns the loss of its long-standing member Ulrich Blau, who passed away on April 1, 2026, at the age of 86. From 1977 until his retirement in 2005, he served as Professor of Logic and Philosophy of Science, shaping generations of students and contributing significantly to the intellectual life of the faculty.

Blau’s work formed an important part of the tradition of analytical philosophy, logic, and philosophy of science established in Munich by Wolfgang Stegmüller. Having received his philosophical training within this tradition, Blau developed over time a highly original logical-philosophical approach. His early works, including his dissertation on epistemic logic (1969) and his habilitation thesis The Three-Valued Logic of Language (1974), belong to the field of philosophical logic. In these and numerous essays, he combined technical mastery of logic and metalogic with a strong emphasis on the role of logic in the analysis of natural language at the intersection with linguistic theory.

Building on the extension of classical two-valued logic to many-valued systems, Blau devoted his philosophical work to the concepts of truth and paradox. He examined these phenomena in their many forms, from the ancient Liar Paradox through their modern resurgence in the work of Georg Cantor and Bertrand Russell, to their central role in contemporary theories of truth. For Blau, however, these technical developments served only as a foundation for addressing deeper philosophical questions, including the mind–body problem and the nature of consciousness.

The culmination of his research is his nearly 1,000-page opus magnum The Logic of Indeterminacies and Paradoxes (2008), developed over decades. In it, Blau moves beyond classical bivalence by introducing multiple truth values, including “indeterminate” and “open,” to account for linguistic and logical phenomena such as indexicality, intentionality, and paradoxes. The result is a complex system he termed “reflection logic,” which establishes a transfinite hierarchy of levels in which truth and falsity dynamically interact. His thesis that all deep paradoxes are ultimately paradoxes of consciousness led him to engage with fundamental philosophical distinctions such as subject and object, certainty and truth, consciousness and being, and mind and body.

His later works, Fundamental Paradoxes, Boundless Arithmetic, Mysticism (2016) and Space, Time and Consciousness: A Brief Introduction to the Ancient Deficit of Physics (2020), further developed and summarized these themes.

The Faculty and the University will honor Ulrich Blau’s memory with deep respect and lasting gratitude.