According to Otto Neurath, the practice of science consists in a large undertaking of setting up and maintaining systems of statements: In unified science we try ... to create a consistent system of protocol statements and nonprotocol statements (including laws). When a new statement is presented to us we compare it with the system at our disposal and check whether the new statement is in contradiction with the system or not. If the new statement is in contradiction with the system, we can discard this statement as unusable ("false'), for example, the statement: "In Africa lions sing only in major chords' ; however, one can also "accept' the statement and change the system accordingly so that it remains consistent if this statement is added. The statement may then be called "true'.