black and white

How do we deal with the tendency to see everything in either black or white? from one extreme to the other? I really like Michael Novak's statement: "Worse than making one mistake is to correct it just when the time for the correction has passed. We must meet each new situation on its own terms, keeping the past in mind but not being predetermined by it." now, should we determine the past? How do historians avoid dogmatism and leaning towards extreme views supported by inflexible arguments? should we follow a balanced approach or should we determine the past by our current historical constructions?