Postdiction - Types

Types

Accusations of postdiction might be applicable if the prediction was:

Vague

The prediction makes a non-specific claim. For example, it predicts a "disaster" of some kind but not what it is. Such a prediction can be massaged to fit any number of events. Likewise, a prediction that does not state dates or places, or allows itself a large window of possible dates can be made to fit many possibilities. A prophecy attributed to Saint Malachy (but widely regarded as a 16th century forgery) claims to predict the succession of Popes by describing each one briefly. However, each description is sufficiently vague that it can be massaged to fit after the fact.

Open ended

The prediction has a very long cut-off date or none at all and therefore runs indefinitely. Many of Nostradamus' quatrains are open-ended and have been postdicted over the centuries to fit various contemporary events.

Recycled

The prediction is reused again and again in order to match the most recent event. Nostradamus' quatrains have been recycled numerous times.

Catch-all

The prediction covers more than one possible outcome. For example, the Delphic Oracle's answer as to whether Croesus should attack the Persians: If you attack you will destroy a mighty empire. Croesus attacked, destroying his own empire.

Shotgunning

The prediction is in fact many predictions, designed to cover a range of events and claim credit even if only one of them happens. For example, claiming that a particular date is "unlucky" and then citing a dozen or so things that might happen on it. See selective thinking.

Statistically likely

The prediction makes a claim for something that happens with enough frequency that a high hit rate is virtually assured. For example, predicting terrorism on any day of the year, or particularly around national holidays, anniversaries (or similar events), or religious festivals.

Unfalsifiable

The prediction makes a claim that is impossible to verify or falsify. For example, a belief arose amongst a few in 2003 that a "Planet X" would pass the Earth in May of that year. When it singularly failed to appear they claimed it was shrouded so that only an "educated eye" could see it and various other excuses, while discounting the most obvious reason — that Planet X does not exist at all in the form predicted.

Unavailable until after the fact

A prediction cannot be verified if there is no public record of when it was made. A famous example was the psychic Tamara Rand, who "predicted" that Ronald Reagan was in danger of someone with the initials "J.H.". The video interview in which this prediction was made was shot the day after the assassination attempt.

Counting the hits and not the misses

The prediction may be part of a series, but is singled out because it can be favourably interpreted, even if the series itself follows the laws of probability. For example, the prediction might correctly state movement on the stock market when previous or subsequent predictions have been wrong.

Allegory

The postdiction resorts to tenuous allegorical explanations to turn literal misses into hits. For example the postdiction might explain that a famous person has suffered a "spiritual" death to explain why they are still walking around despite a prediction that says otherwise.

Moving the goalposts

The event must be "shoehorned" to fit the prediction because it differs in some significant way. For example, the prediction predicts an earthquake on one day when in fact it happens on a different day. Once again, Nostradamus supporters occasionally use this technique, as Nostradamus supposedly predicted the founding of the Institut Pasteur in 1888 (it was actually a year later) and the September 11 terrorist attacks on the 45th parallel(actually significantly southwards).

These types are not exclusive, so a prediction could be vague, statistically likely and open-ended at the same time.