Sentence:  [P]hilosophers of the time [early 20th century] were primarily concerned with <WSD>epistemology</WSD> and the foundations of the sciences; they often spoke as if we were separated from the real world by a screen of "representations" or "sense-data"; they tended to regard our approach to the world as one of disinterested observation. 
Meaning of the word marked with <WSD> tags:  The branch of philosophy dealing with the study of knowledge; theory of knowledge, asking such questions as "What is knowledge?", "How is knowledge acquired?", "What do people know?", "How do we know what we know?".