The word "truth" is generally taken to imply that what is true must be about something which exists or is "real." This is often called the "correspondence theory of truth", according to which the true statement is true because it represents things as they really are, the "facts" correspond to what the law says, whereas the false statement is false because it fails to do so. According to this notion of "truth" as referring to a representational relation between statement and reality, since all theoretical statements go beyond the purely observable and make statements about unobservable processes or properties or objects, perfected scientific theories are really true descriptions of this "unobservable" world which is often said to "lie behind the observable phenomena." This reality is often believed to stand in some causal relation to what is observed. In short it was held by the consensus that if one holds that such statements are true in this correspondence sense, then one must hold that such unobservable entities are the real causes of observable phenomena. This position is known as scientific realism. Many defenders of the consensus were scientific realists in this sense. However, one could accept all the elements of the consensus and argue that only observation statements are true or false; theoretical statements are neither true nor false, but are accepted because of their use as "instruments" enabling the scientist to infer from one set of observation statements, those stating the antecedent conditions, to another set of observation statements, those describing the observed phenomenon predicted or explained. This view, often called instrumentalism, is a specific form of "anti-realism," and was defended by some members of the consensus. Thus in one sense the consensus was neutral on realism versus anti-realism, but in another sense, namely that realism demands a commitment beyond what the consensus agreed upon, it is fair to regard the empiricist consensus as anti-realist, at least in spirit, though many of its defenders would have called themselves realists.