American physicists Russell Targ and Harold Puthoff once conducted an experiment in 1972 with subject Ingo Swann and the following is what happened according to their reports:
Swann focused his attention on a magnetometer, which detected the rate of decay in magnetic fields, and the output of the magnetometer doubled for about 30 seconds. When asked to stop thinking about the device it’s output fell back to normal but when Swann spoke of the magnetometer it again showed a spike.
Given that no one denies these experiments did take place what conclusions, if any, should we draw from these facts alone? Should we believe that the events are merely a fabrication and that such experiments never took place? Can we conclude that what they implied, Swann psychically controlled the magnetometer, necessarily occurred?
While nearly everyone will acknowledge without some reason to doubt the events really happened it’s reasonable to conclude that these experiments took place but the same can not be said for assuming the events took place as described. Given just these facts it would be fine to conclude it’s possible it happened as Targ and Puthoff described but it’s not at all reasonable to say it necessarily is the case or even to believe that it occurred this way. Swann could have in fact controlled the magnetometer with his mind but the magnetomter could also have been malfunctioning, there could have been interference, there could be missing details from the story which demonstrate that this was an elaborate trick, etc.
Without repeated tests in which multiple magnetometers were used, the testing area checked for possible interference, Swann examined for all possible trickery, etc. you’d merely be taking their reports that it happened as proof that it happened. In order to conclude the best explanation is that Swann really was controlling the magnetometer you’d have to weigh the array of possible explanations, determine what would rule out each explanation, see which explanation fits best with the observed phenomena and all similar phenomena and so on. To believe Swann really did control the magnetometer with his mind without some way to subject the claim to this type of critical analysis would be to reject all your experience, and all known experience, about how the world works simply because someone reported something which seemingly defies explanation. You would, in other words, be believing without justification. The fact that in this example, taken from James Randi’s book FlimFlam!, we have additional details which clarify that the events didn’t really occur as described is beside the point.
This is a problem that underlies all miracle claims from holy books. Without some way to test the subjects and verify the abilities claimed you’d simply be taking the human author’s word as proof that these miracles indeed occurred as reported. Unlike the Targ and Puthoff experiment, which happened in 1972, these miracle claims come from a pre-scientific age in which we can be all but assured no proper cross-examinations of the events took place let alone the events described being later tested in a controlled setting. It’s not hard to imagine that a modern magician with many simple illusions would be hailed as divine in the times of holy books because people simply didn’t have a firm grasp on the nature of reality or the methods by which they can be deceived (indeed many magicians use simple tricks like this today to fool people into believing they have paranormal powers). This doesn’t even account for the overwhelming possibility that during that the oral or written traditions that proceeded the accounts available to us today were consciously and unconsciously bolstered and/or completely fabricated.
This is why the amount of evidence that those in the times of the alleged miracles really believed these miracles occurred is not relevant to establishing they really did occur or that it is reasonable to believe they occurred. Without some way to subject the claims of miracles to the type of controlled analysis required to rule out alternative explanations all you have is claims of miracles and such claims are no more worthy of belief than Targ and Puthoff’s claim that Swann really did control the decay of a magnetic field with his mind. Unless you are prepared to accept all stories like those of Swann at face value, which would include many mutually exclusive claims, you certainly shouldn’t accept those of the Bhagavad Gita, the Qur’an, the Bible or any other holy book.