總瀏覽量

2011年9月1日 星期四

Can a Negative be Proven?

In discussions with Christians who wish to argue that their God truly exists, one of their favorite fall back positions is that even though they cannot advance positive arguments to prove "that God exists" , neither can the atheists positively prove "that God does not exist". How good is this argument?

It seems that the basis of the Christians' claim is that it is impossible to prove a negative. However, according to David Ramsay Steele, " we can indeed prove negatives and we do so all the time." ("How to Prove a Negative" in Atheism Explained: From Folly to Philosophy 2008 "AE" 167). He argues that if we cannot prove a negative, then we cannot prove a positive either since every positive implies an infinite number of negative statements.e.g. if I prove that "all the marbles in this box are white", then I automatically also prove that "none of the marbles in this box are blue, purple, red..." and also that "none of the marbles in this box are transparent" etc.

What people mean when they say "we can't prove a negative" is that given a limited number of observations, we often can't demonstrate that certain things do  not exist because an exhaustive search is impracticable. Thus we can't prove that fairies do not exist because although reports of fairies have been convincingly explained on the basis that there are no fairies and no credible observation of a fairy has been documented, still, we cannot rule out the possibility that fairies might be very shy and very good at hiding, perhaps just confined to a few remote locales and also able to turn invisible at will and therefore the possibility remains that some fairies have eluded all observations.

No one doubts that mammoths became extinct a long time ago. Had they survived, it is very likely that they would have been seen at least by some people but since they have not been seen alive in the past 10,000 years, they have not survived. You can of course question the first proposition "had they survived..." or alternatively question the second proposition "they have not been seen for the past 10,000 years". But if so, you can equally always question the premises of any proof.   

To Steele, observation is not the only way to prove that an entity does not exist. Sometimes, we can prove that something does not exist because it is logically impossible or self-contradictory that it does e.g a square circle. We can prove that a perpetual motion machine does not exist because it contravenes the laws of physics. In such cases, it is much easier to prove a negative than proving a positive.  We know that a Pegasus ( a horse with wings) does not exist because wings of that length could never support as heavy a body as that of a horse to be carried through the air. Likewise we never see the kind of giant wasp in H.G Well's The Food of the Gods because the wings increase by area whereas the mass of its body increase by volume and the way the insect breathes through its skin cannot be scaled up beyond a certain point without some other drastic alteration in its anatomy.That is one of the reasons we never see any giant insects.

Steele points to a second way the theists use to stop their God from being proved not to exist. They define the qualities of their God in such a vague way as to be beyond full comprehension.

A third way is to add ad hoc adjustments to the qualities of their God. Christians say that the intentions of their God is unknowable in principle and they try to rationalize what they cannot otherwise explain e.g. the existence of natural evil by claiming that somehow, overall, this world is still consistent with the idea of their God being a God who is all good by pointing to all the peripheral goods which accompany what we would otherwise consider bad or evil.Thus the defender of an all loving, all powerful God may tell us that
earthquakes and epidemic disease are engineered by fallen angels, whom
God could not keep in line because "he just had to guarantee" their
free will. Steele says, "it is always possible to rescue God's existence from refutation by 'redefining' God. Proving the "non-existence of God" is always proving the "non-existence of God defined in a specific way" and it is therefore surprisingly similar to theological debates on 'God's nature'".

A fourth way the theists employ is to deny the premises of the proof. They can say that what other scientists regard as a scientific principle or law or theory is not in fact such a principle or law or theory or that the same is otherwise not yet proven. e.g.that man and the other plants and animals in it are not the result of Darwinian evolution but were directly created by God, that the world did not come about as a result of quantum fluctuation at the beginning of the universe but was created by God as stated in the Genesis. In regard to the example he cited with regard to Well's giant wasp, they would claim that the aeronautic engineers are wrong about the mechanics of flight or the biologists are wrong about the breathing equipment of insects.

Steele says, "The conclusions of any proof can always be avoided. This has nothing to do with proving a negative: we can do just the same with proving a positive. " and asks; "Does this mean the whole exercise of proving something is pointless?" (AE 169) Not necessarily. Why? Because, he says, "every proof is an argument and every argument can be presented as a proof. By framing an argument we put the defender of the non-existent object in a position he may not have expected.... Upon reflection, the defender may decide he doesn't wish to defend it any more." Or "other people, listening to his arguments, may find them less persuasive now they see what other  assertions have to be made to rescue those arguments." (AE 169) Thus the defender of a perpetual motion machine will have to deny the first and second laws of thermodynamics.

Steele complains in particular that the traditional Christian God has chosen to hide himself. He quotes: "How long, God? Will you hide your face forever? Psalm 89:46". He says that although the Torah has numerous reports of humans seeing various parts of God's anatomy (Genesis 32:30; Exodus 33:23), these are now always taken "metaphorically." and even John says "No man has seen God at any time" (Jn. 1: 18). It is obvious therefore that God cannot be perceived by sight, smell, sound or touch nor can his activities be detected by any of our most sensitive scientific instruments.

Even devout believers often report so-called "dark night of the soul", including Mother Teresa, when they felt they should believe but couldn't. According to Steele, we can easily imagine a world in which no one or hardly anyone would seriously doubt that there was a God because his existence would frequently be corroborated by experience, as David Hume claim: "Suppose...that an articulate voice were heard in the clouds, much louder and more melodious than any which human art could ever reach: Suppose, that this voice were extended in the same instant over all nations, and spoke to each nation in its own language and dialect: Suppose, that the words delivered not only contain a just sense and meaning, but convey some instruction altogether worthy of a benevolent being, superior to mankind: could you possibly hesitate a moment concerning the cause of this voice? And must you not instantly ascribe it to some design or purpose? (Hume Dialogues in Writings on Religion ed. Anthony Flew 1992 213). "God could manifest himself in human form, just as he is often described in Genesis. it would be quite easy for the human form to say and do things which made it clear that it was the embodiment of God", says Steele (AE 171). Has the Christians not been taught that Jesus is the "incarnation" of God as God the Son? He suggests further: "God could take a non-human form, such as a gleaming cylinder topped by a halo, available for conversation with humans and full of fascinating and sometimes helpful information. Or God could dictate a book to someone, not filled with the human ignorance of the Bible or the Qu'ran but containing ample information which only an entity vastly more knowledgeable than any human could have set down." (AE 171-171).

Steele does, however, accept that the fact that God is not observable does not of itself indicate that he does not exist because we often accept the existence of things which we have not perceived e.g. quarks and magnetic fields. Thus most physicists believe that the greater part of the universe is made up of "dark matter" which no one has yet observed either visually or without the aid of special instruments. (AE 172) It may be difficult to prove the existence of something which is not directly observable as Louis Pasteur found out when he discovered the bacterial origin of many diseases. But Steele argues since God is supposed to be an intelligent mind who wants us humans to believe that he exists and he is also said to be all-powerful, he could therefore easily make his existence clear to humans. God is said to be almighty, so he can do any one thing as easily as he can do any other. So revealing himself in an unambiguous manner can pose absolutely no difficulty to him. But the fact is that he hasn't done so in any clear and unambiguous manner. So this gives rise to what has variously been called "the Argument from Silence", "the Argument from Divine Hiddenness" or the "Argument from Non-belief" which runs roughly as follows:

1. God could easily have shown strong evidence of his existence to human beings, strong in the same way that the evidence for the existence of trees, stars and other people is strong.
2. We can take it that God wants humans to believe that he exists,
3. Therefore God must have wanted to give strong evidence of his existence to humans.
4. But human beings have no such strong evidence that God exists.
5. Since God has not shown human beings strong evidence of his existence, therefore God does not exist.  (AE 172-173)

Steele anticipates one of the Christian responses: "How dare you make demands of the Almighty?" but he says that if so, then the Christian has missed the point. He explains: "The atheist is not asking God to do anything. The atheist is merely scrutinizing the claims of the theists, to see what they're worth because the atheists are just concerned with the "possible truth" of some claim, so they have to test that claim by looking at what the claim would imply IF it were true. (AE 173)

The theists may argue that God has chosen deliberately not to reveal himself for his own reasons of which we are ignorant. But William Lane Craig, one of the staunchest defenders of the Christian faith, does not agree. He says, "Although I've found that atheists have a hard time grasping this, it is a fact that in the Christian view, it is a matter of relative indifference to God whether people (merely) believe that he exists or not. For what God is interested in is building a love relationship with you, not just getting you to believe that he exists (William L Craig and Walter Sinnott-Armstrong  God? A Debate between a Christian and an Atheist 2004 109) . Steele thinks that Craig is being "idiosyncratic" here. He asks "If they think God doesn't care much about humans believing in his existence, why did the Christians spend thirteen hundred years torturing to death anyone who disputed it?". (AE 174)  He cites in support of his view: "He who has believed and has been baptized shall be saved, but he who has disbelieved shall be condemned." (Mk. 16: 16). To Steele, belief in God is a prerequisite of any love relationship with God. If that is not important, why does Craig spend so much of his life trying to convince people that God exists?

Steele then uses the rest of the chapter to refute what he calls the "moral freedom defence" (AE 174-178), which has only peripheral relevance to the thesis embodied in the title of that chapter and finally returns to that principal thesis. He says that theists sometimes respond to criticisms of their claim by saying that God is far beyond our understanding, e.g that God has a purpose unknown to us in "pretending" not to exist. To my experience, this is often the case. But Steele claims that Christians also claim that God cannot divulge that purpose to us. Do they? Whether or not he is right in this, I agree with him that "Everything the theist tells us about God and every possible case he can make for the existence of God, appeals to our understanding of God and of his motives, character and qualities...If we cannot begin to understand God's purposes, then all the theist's assertions about God are in vain. Theism requires that God be comprehensible in broad outline, if not in perfect detail."

For the ordinary folks, what is important is how religion may help them cope with life here on earth: whether it can offer them hope when they are faced with the such universal existential crises like uncertainties hovering over such stressful occurrences as the sudden and unexpected arrival of possibly fatal sickness, the risks of unemployment, the fate of their finances or those of their mates, their parents, their brothers and sisters and their closest friends and consolation for their loss upon their departure whether temporary or permanent and also the fear often associated with their death or mortality. All too often, their belief in God is based upon an "unexamined metaphysical presupposition" that God truly exists and about his claimed attributes. They believe on the basis that what people in whom they have trust and confidence and upon whose good will and honesty they have little reason to doubt( e.g. their parents, teachers, ministers, monks, nuns etc.) have taught them to be true and on the basis that the Bible is "the word of God" or is written by people "inspired" by God. But careful examination of such presuppositions often reveal numerous contradictions, logical inconsistencies and inadequacies. For the believer, "faith" is therefore a constant uphill struggle if they bother to think at all, something upon which Kierkegaard has given a great deal of thought already in the 19th century.