 One traditional debate in the philosophy of science is whether scientific observation is permeated with the theory of the scientist, or theory-laden (see the entry on   theory and observation in science).   As Raftopoulos and Zeimbekis point out, when asking whether observation is theory-laden, the answer will depend in part on what it means for a subject to possess a theory (2015: 18). On their view, theories can be tacit, rather than just “having a set of beliefs and concepts” (p. 18).