The Outside View that Daniel Kahneman talks about in his book Thinking, Fast & Slow, is a specific remedy to a problem known as the planning fallacy (i.e.) the inability of people to make predictions. The planning fallacy is part of a larger problem of optimism bias. What is optimism bias? Simply put, people are generally more optimistic than they should be. For example, it is well known that most people think they are better than average drivers, an impossibility. It stems from a general dose of overconfidence not warranted by the situation on hand.
The best example of overconfidence is a study that Kahneman cites of CFOs of large corporations. They were asked to estimate the returns of the S&P Index over the following year. The data were collected over a number of years and hence there was ample opportunity to correlate it with the actual performance of the Index in the following year. Any guesses as to this correlation, given that the respondents should have been expected to have special insight in this matter? It was almost exactly zero, slightly less, in fact! And they seemed to have no idea their forecast was that bad.