Sunday, September 05, 2021

Overestimating The Prior Improbability Of Miracles

Stephen Braude wrote:

First, it is moot whether psi phenomena violate any important scientific theory. Only from an already suspect reductionistic perspective would they seem to pose a threat to received science. It is more plausible that psi phenomena, like organic phenomena and the phenomena of consciousness generally, simply fall outside the domain of physics. Second, even if psi phenomena did violate some major scientific law(s), there is nothing sacred about received science. Like the received science of days past, much of it may require modification or rejection, even if only to countenance everyday mental processes such as volition and memory. Third, subjective probability assignments concerning scientifically anomalous phenomena carry little weight, as the history of science amply demonstrates.

Moreover, we know very little about ostensibly paranormal phenomena (especially, I suppose, if they are genuinely paranormal) but a great deal about misperception, naiveté, fraud, etc. But in that case, our assessments of the probability of the latter should be given greater weight than our assessments of the probability of the former. After all, we often have a solid basis for judging the likelihood of misperception, etc., occurring in spontaneous cases. But we have virtually no basis for deciding the likelihood of an event occurring - in the absence of fraud, misperception, etc. - that at least appears to violate some fundamental scientific law or metaphysical assumption. We do know, of course, that phenomena discovered in the past have deeply changed the course of science, and we know that phenomena considered impossible or highly improbable on received scientific principles have been found to be possible or not so improbable after all. So we know that genuine scientifically anomalous phenomena may occur, some of which eventually get incorporated into the science of the day. But earlier on, when the phenomena are still extraordinary and poorly understood, we lack the kind of information customarily needed to assess the probability of their having occurred. To judge whether a given event is likely in a particular circumstance, we must first know something of the event's nature and limits. That is how we determine the likelihood of misperception, fraud, etc. We know what sorts of situations might motivate fraud or encourage misperception, and we can make reasonable and well-informed judgments about their likelihood in the circumstances in question. In fact, we have a substantial and clear background of data to which we can appeal when making these judgments. But it is just this sort of background information that we lack in the case of ostensibly paranormal events. So it seems reasonable to decide the likelihood of an ostensibly paranormal event having occurred on the basis of the evidence against the occurrence of misperception, fraud, etc. (The Limits Of Influence [Lanham, Maryland: University Press of America, Inc., 1997], 46-47)


He goes on to quote some comments from C.J. Ducasse:

…assertions of antecedent improbability always rest on the tacit but often in fact false assumption that the operative factors are the same in a presented case as they were in superficially similar past cases. For example, the antecedent improbability of the things an expert conjurer does onstage is extremely high if one takes as antecedent evidence what merely an ordinary person, under ordinary instead of staged conditions can do. The same is true of what geniuses, or so-called arithmetical prodigies, can do as compared with what ordinary men can do. And that a man is a genius or a calculating prodigy is shown by what he does do, not the reality of what he does by his being a genius or prodigy. This holds equally as regards a medium and his levitations or other paranormal phenomena. (47)


Braude then comments:

It would be almost transcendentally foolish to maintain that the unprecedented mnemonic abilities reported by Luria (1968/1987) are unlikely to be genuine, due to their antecedent improbability (based on the population of normal human beings). With reasoning such as this, we could forever avoid acknowledging the existence of exceptional human abilities. But then it is presumably equally indefensible to distrust nearly a quarter-century's worth of reports of decently-illuminated table levitations by D.D. Home, on the grounds that the antecedent improbability of that ability is overwhelmingly high. (47)

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