Thus, logic and mathematics are important in determining “what is,” though not necessarily implying what is. “What is” must be consistent with logic,… - Robyn Dawes

People treat reason as if it were the most minor and harmful aspect of a whole human being. It is as if a soldier standing guard were to say to himself: “What good would my rifle be I were now to be attacked by a dozen enemies? I shall therefore lay it aside and smoke opium cigarettes until I doze off.”

As discussed in Chapter 7, we often substitute a good (internally generated) narrative or story for a comparative (“outside”) analysis when we attempt to understand something unusual. We also often substitute pure association for comparison. This reliance on coherent “explanations” provides what is really an illusion of understanding, rather than understanding.
In this chapter, I present the other side of the coin. That is, even when we have a perfectly valid statistical explanation for a phenomenon, we may ignore it because no “good story” accompanies it to persuade us that we should believe it.

The situation is very simple. Familiarity leads to availability and often to accuracy as well; hence availability is used as a cue to accuracy.
The problem is that mere assertion and repetition also leads to availability, whether or not this assertion and repetition involve reality, as familiarity generally does. Thus, the “big lie” of Nazi propaganda minister Joseph Goebbels was based on the idea that if something is repeated often enough, people will believe it—in large part simply because they have heard it before…
Goebbels apparently believed that providing a credible source, for him the German national government, was a critical component in having the repeated statements believed. Subsequent research has shown that the credibility of a source is not a necessary condition to develop beliefs…
Worse yet, mere repetition—which creates an availability bias due to familiarity, can also make people confident of their own decision making in the absence of any feedback that they have made good decisions.