In Göttingen, he encountered David Hilbert and was impressed by his program attempting to base all mathematics on solid logical foundations derived from a limited number of axioms.

[7] Within a year of completing his doctorate, the increasingly repressive and anti-semitic Nazi regime in Germany had prompted Hempel to emigrate to Belgium as his wife was of Jewish ancestry.

He believed that the term "positivism," with its roots in the materialism of Auguste Comte, implied a metaphysics that empiricists were not obliged to embrace.

His examination of Semmelweis's systematic discovery in addressing a scientific problem provided a historical context for Hempel's own reflections.

He considered Semmelweis's approach as a pivotal example of how empirical evidence and inductive reasoning play a crucial role in the development of scientific knowledge, further enriching his perspective on logical empiricism.