What did Rudolf Carnap argue in The Logical Structure of the World?

In his 1928 work The Logical Structure of the World (originally titled Der logische Aufbau der Welt), Rudolf Carnap developed a rigorous version of the empiricist "reducibility thesis".12

Carnap argued that all terms used to describe actual or possible empirical facts are fully definable by terms referring exclusively to immediate experience. Under this framework, he proposed that all empirical statements are fully translatable into statements about immediate experiences. This system, known as constitution theory, envisioned a hierarchy where undefined, private experiential concepts form the ground level, with more complex scientific concepts built upon them using symbolic logic.21

By demonstrating how scientific concepts—such as "atom" or "gene"—could be "reduced" to experiential data, Carnap sought to provide a precise, systematic grounding for empirical knowledge. This project was central to the early development of logical positivism, as it aimed to establish a "scientific world view" by applying the precision of modern logic to philosophical inquiry.12