How did Rudolf Carnap explain the relationship between experience and empirical knowledge?

Rudolf Carnap, a central figure in logical empiricism, interpreted the relationship between experience and empirical knowledge as a systematic-logical issue regarding the evidential grounding of assertions. Rather than focusing on the psychology of how humans form ideas, he analyzed how scientific and everyday language relates to the data of immediate experience.1

Carnap’s approach evolved over time:

• Strict Reducibility: In The Logical Structure of the World, he argued that all empirical terms are fully definable by, and translatable into, statements about immediate experience.1
• Liberalized Empiricism: Later, in "Testability and Meaning," he proposed that scientific terms are only partially definable through "reduction sentences" and "observation sentences." He emphasized that empirical statements are not strictly proven but rather receive varying degrees of "confirmation" through direct observation.1

Carnap maintained that statements lacking observational implications are empirically meaningless, a testability criterion he used to reject speculative metaphysics. Through physicalism, he further argued that all empirical science can be reduced to the language of physics.1