Monday, 9 March 2009

Hume and Probability

Response to edulike comment on RD.NET, re the historicity of the resurrection:

You are taking the stance that "if there is any doubt, because of the incredible nature of the events depicted, then I will not believe they occurred until I have examined every shred of evidence".

*Absolutely* not.

Quite the contrary, I am open to the possibility that the events occurred. Because of the timescales we necessarily don't have the sort of evidence that could *prove* matters either way. So what do we do? As is often the case, David Hume provides the answer:

A wise man, therefore, proportions his belief to the evidence. In such conclusions as are founded on an infallible experience, he expects the event with the last degree of assurance, and regards his past experience as a full proof of the future existence of that event. In other cases, he proceeds with more caution: he weighs the opposite experiments: he considers which side is supported by the greater number of experiments: to that side he inclines, with doubt and hesitation; and when at last he fixes his judgement, the evidence exceeds not what we properly call probability. All probability, then, supposes an opposition of experiments and observations, where the one side is found to overbalance the other, and to produce a degree of evidence, proportioned to the superiority. A hundred instances or experiments on one side, and fifty on another, afford a doubtful expectation of any event; though a hundred uniform experiments, with only one that is contradictory, reasonably beget a pretty strong degree of assurance. In all cases, we must balance the opposite experiments, where they are opposite, and deduct the smaller number from the greater, in order to know the exact force of the superior evidence. (Of Miracles)

We have no choice, if we are being scientific, but to base our determination of the historical events based on what is most likely; *probability* has to be used. This is how all good historians *must* operate. This is not to exclude other explanations as *possible*; there are any number of possible explanations for stories we hear. What we are trying to establish is which is the most *reasonable* explanation.

So what is the effect of this principle? It is often stated as 'extraordinary claims require extraordinary evidence', and *must* be the way to proceed, to be scientific.

You say:

Hence there are no words like certainty and probability in my reasoning.

Well, exclude certainty, perhaps, but if you don't use probability you are simply not acting scientifically. Now that may be fine for you, since you don't think you can answer this scientifically; but it's clear we *can* evaluate the *evidence* scientifically, and I can demonstrate your position is *less reasonable* than mine. Not *unreasonable*, necessarily, but less reasonable. You are adopting the NOMA principle beloved of scientists who believe; cognitive dissonance by another name :-).


Post a Comment