Skeptics like to say that "extraordinary claims require extraordinary evidence." (The phrase was apparently coined by Carl Sagan, channeling Hume and LaPlace.) The thing is, who gets to decide what claims are considered extraordinary?
The principle appears to have been first explicitly formulated by philosopher Michael Scriven in his Primary Philosophy
(1966). The idea is that a claim that strongly contradicts previous human experience is to be doubted until exceptionally strong evidence is provided. I don't yet own Primary Philosophy
, but I do own a book that summarizes Scriven's argument. It is God and the Burden of Proof
by Keith Parsons. This is how Parsons explains Scriven's idea:
"When a claim asserts the existence of something that is greatly at odds with our previous experience, we rightly regard the claim as very probably false until we are given truly strong evidence in its favor. Thus, we are not too skeptical when, in reading the newspaper, we find that the world high-jump record has been exceeded by a centimeter or two. However, we would indeed be very skeptical, and rightly so, if we read...that someone had leapt a tall building in a single bound..."
"...All of God's alleged powers and attributes are of a very extraordinary sort. As defined by orthodox theists, God is not constituted by energy or matter, he does not exist in space and time (though he can act in space and time), and he created the universe though he himself is uncreated. Further, God is said to be all-powerful, all-knowing, and perfectly good...God is entirely different from the finite,...material sorts of beings that we encounter in the natural world. Therefore, if we are to judge how likely something is to exist on the basis of what we have previously known to be the case, we must rate the likelihood of God's existence very low indeed. Further, since extraordinary claims must be supported with extraordinary evidence, we must insist on very solid evidence indeed before we affirm the existence of God."
This is a fair point, as I see it, and not necessarily threatening to "religious" beliefs. The sophisticated religionist can embrace this as a purely epistemological principle and still justify his or her religious beliefs in any number of ways. For example, a thinking Christian mystic might argue from spiritual pragmatism: He or she might say, "Yes, the existence of a divine creator seems unlikely right now, given what we currently know. However, whether this God is real or not, the idea of him works within the context of the spiritual path I follow, as a model of moral perfection, as a source of hope, inspiration, and perseverance, as a powerful means of spiritual transformation, etc. This God is real enough to me and of great value to me, whether or not he actually exists."
A Buddhist still has a wealth of evidence with which to argue for the survival of the consciousness stream, even though rebirth isn't part of common (ordinarily remembered) human experience. He (or she) might begin by pointing out some of the weaknesses in physicalism in order to clear the way for consideration of other possibilities: we lack any good explanation as to how a physical system can produce subjective experience or awareness or even an experimental means to rule out alternative models of consciousness. As skeptical neuroscientist Sam Harris surprisingly puts it, "The idea that brains produce
consciousness is little more than an article of faith among [some] scientists at present." Then he might point to the case made by physicists such as Eugene Wigner, Max Planck, and many others, on the basis of the evidence of quantum mechanics, that consciousness is a fundamental force of the universe, evidence that led physicists Paul Davies and John Gribbin to declare that "materialism is dead" (e.g., the laws of quantum mechanics can't be formulated without reference to consciousness, indeterminate quantum phenomena actually "exist" as a range of possibilities and "choose" a specific option, such as a location, only after they are observed, attacks on the Copenhagen Interpretation that is the source of this perspective have consistently strengthened the evidence for it, etc.). Moreover, he might observe that neuroscientists have located numerous aspects of the mind, both simple and complex, in the brain. These tend to be clearly brain-dependent, in that they can be created by stimulation of the corresponding part of the brain and destroyed by damage to the brain. Yet consciousness itself seems to be the one thing that has yet to be located therein (although transitions between levels of consciousness do produce changes in the frequencies of brain waves). To borrow and repurpose an atheist argument of N.R. Hanson, scientists can look and evidently find the rest of the elements of the mind at all degrees of complexity in the human brain (from visual perception processing to intelligence to language processing to emotion to imagination to creativity and so forth), but continually looking in this particular place throughout the decades and not finding a physical basis of consciousness itself would seem to place it in a category similar to that of Big Foot and the Loch Ness monster. It gives us a good reason to begin to doubt that a physical basis is there. And so on...