Any prediction is a hypothetical statement about future existential relationships. The circumstances and consequences surrounding the making of professional prophetic statements has always varied considerably. Ancient oracles covered their track linguistically by simply making ambiguous predictive statements which could be justified by interpretation no matter what actually eventuated. Court astrologers, with a strong sense of self-preservation, included several options when they predicted the future from astral configurations. In proportion to the potential rewards, they risked both their vocation and even their lives by biasing their prophesies towards their clients own desires, expectations and abilities. Encouraging a client towards self-belief and thence to the self-fulfilment of a prophesy is a potentially rewarding but hazardous exercise.

Prophesies based upon scientific models are called predictions and serve to test the validity of the model. As the various periodic astronomical models were established, for instance, the predictions became sufficiently accurate for most practical applications and the anomalies were normally deemed to be insignificant. The predictions of sunrises, tides, eclipses, phases of the moon and the position of comets, rarely give cause for the prophets to be embarrassed, so that their reputation remained secure. For untested models of new theories, predictions simply function as a means of confirming or denying the accuracy of the model. They serve to evaluate the truth or falsity of those assertions which constitute a statement of the model. Nothing more is at stake than the validity of the model... except perhaps some egos and a big chunk of funding.

Modern prophets use probability theory to ensure the accuracy of their predictions. Having to make do with a deficiency of data and over-simplified models, contingency preparations need to be put in place with considerable care. Those predicting the occurrences of certain chaotic events like the weather, economic trends, earthquakes or volcanic eruptions for instance, all need some sort of insurance policy... either a substantial resource of plausible explanations for failure, or the support of inconvenient results from esoteric probabilistic theory. It is the theory of expectation probabilities that provides the most secure insurance of reputation. By indicating the expectation of a predicted event as a percentage probability, the prophet is insured against error. Whatever outcome eventuates... barring any really nasty perturbations like the end of the world... it will be an outcome promoted by the prophet. The weather forecaster that predicts that... 'there will be a 25% probability of rain'... cannot be wrong. The probability of success has been specified as 25%. The probability of failure has been specified by implication as 75%. If it does rain, the forecaster was right. If it does not rain, the forecaster was right. Whatever happens, the outcome has been allowed for and the reputation of the prophet remains intact. The prophets concerned can retain their integrity, continue their profession, and sustain their source of income. Meteorologists, economic forecasters and political pollsters, are probably without peer in this respect.