McMullin states that scientific realism is the belief that �the long-term success of a scientific theory gives reason to believe that something like the entities and structure postulated by the theory actually exists� (1984: 26, italics removed, in Hunt, 2003: 171). Scientists should, in other words, seek theories that hold up over time, recognize the fallibility of theories, accept that reality may not be exactly as theorized, and believe that reality exists independently of its being perceived. The belief in an independent reality was shared by the logical positivists, for whom theories must be based on absolute certain knowledge (Hunt, 2003: 70). �Certain� knowledge implies permanence and infallibility of theory, in opposition to the ideas of scientific realists. A basic difference, therefore, between the two philosophical stances is the acceptable level of precision. A scientific realist may accept broad uncertainty in developing theory, and thereby, s/he will not demand a high level of precision in empirical study. On the other hand, a logical positivist would demand precision in theory and empirical effort. Hunt (2003) describes the logical positivist movement as completed and states that modern science has moved to a stance of scientific realism.