Let us not, in the pride of our superior knowledge, turn with contempt from the follies of our predecessors. The study of the errors into which great minds have fallen in the pursuit of truth can never be uninstructive.”

– Charles Mackay
Extraordinary Popular Delusions and the Madness of Crowds


Delusions are often viewed as reflecting some deficiency in reasoning ability. The risk of thinking about delusions in this way is that it encourages the belief that logical, intelligent people are incapable of delusion. An examination of the history of financial markets suggests a different view. Specifically, faced with unusual or extraordinary price advances, there is a natural tendency (particularly in the presence of crowds, feedback loops, and potential rewards) to look for explanations. The problem isn’t that logic or reason has failed, but that the inputs have been distorted, and in the attempt to justify the advance amid the speculative excitement, careful data-gathering is replaced by a tendency to confuse temporary factors for fundamental underpinnings.

While true psychological delusions are different from financial ones, a similar principle is suggested by psychological research. Delusions are best understood not as deficiencies in logic, but rather as explanations that have been logically reached on the basis of distorted inputs. For example, individuals with delusions appear vulnerable to differences in perception that may involve more vivid, intense, or emotionally-charged sensory input. While those differences might be driven by neurological factors, the person experiencing these unusual perceptions looks to develop an explanation. Maher emphasized that despite the skewed input, the delusions themselves are derived by completely normal reasoning processes. Similarly, Garety & Freeman found that delusions appear to reflect not a defect in reasoning itself, but a defect “which is best described as a data-gathering bias, a tendency for people with delusions to gather less evidence” so they tend to jump to conclusions.

The reason that delusions are so hard to fight with logic is that delusions themselves are established through the exercise of logic. Responsibility for delusions is more likely to be found in distorted perception or inadequate information. The problem isn’t disturbed reasoning, but distorted or inadequate inputs that the eyes, ears, and mind perceive as undeniably real.

Let’s begin by examining the anatomy of speculative bubbles. We’ll follow with a discussion of three popular delusions that have taken hold of the crowd, and the premises that drive them: the delusion of paper wealth, the delusion of a booming economy, and the delusion that is Bitcoin.

The anatomy of speculative bubbles

Across centuries of history, speculative financial bubbles have repeatedly emerged from the seeds of distorted financial environments, where speculative behavior increasingly produces self-reinforcing feedback. Specifically, the speculative behavior of the crowd results in rising prices that both impress and reward speculators, and in turn encourage even greater speculation. The more impressed the crowd becomes with the result of its own behavior, the more that behavior persists, and the more unstable the system becomes, until finally the flapping wings of a butterfly become sufficient to provoke a collapse, launching a self-reinforcing feedback loop in the opposite direction.

The 1929 bubble was built on the foundation of real economic prosperity during the roaring 20’s, but the late stages of that boom were largely fueled by debt and easy money. Observing the persistent market advance, investors largely ignored the contribution of their own speculation in producing that advance. Rather, as traditional valuation measures became increasingly stretched, the first impulse of investors was to try to justify the elevated valuations in novel ways, which gradually became nothing but excuses for continued speculation. As John Kenneth Galbraith wrote decades ago in his book, The Great Crash 1929: