Watching the film Final Destination, I think about what causality is? Can “premonition” be given a “scientific explanation”? Can “supernormal abilities” be justified within scientific epistemology?
1.Laws, causality, time
Hume pointed out that causality is only a “habit,” and he was not wrong.
When we see “2, 4, 6, 8, ___, …,” even the dullest primary school student knows how to do this kind of “find the pattern and fill in the number” problem; they will unhesitatingly write “10” in the blank, while slightly cleverer students will sum it up into a universal “rule” — “the nth number is 2n.” This problem is far too simple, but its basic principle is exactly the same as the way scientists induce “natural laws”! That is, “finding the pattern” in a series of empirical facts or experimental data, summarizing the pattern, and making predictions.
However, middle school students no longer do “find the pattern and fill in the number” problems, because some of the cleverer students have already figured out that there is no determinate answer to such pattern-finding problems: there are infinitely many answers, and any number can be an answer!
From 2, 4, 6, 8 we can summarize the rule “the nth number is 2n,” but why not the integer part of 2.2n? Or “3n4-40n3+180n2-303n+162”? To identify the nth number as 2n is nothing but a matter of “habit.” We habitually favor the simplest, most readily available answer, but that is not necessarily the true answer; Newton’s laws being surpassed by relativity proves this point.
We see “the sun shines — the stone grows hot”; we often observe these two phenomena happening one after another, and so we identify the sun’s shining as the “cause” of the stone’s heating. But in any case, we can only observe phenomena a finite number of times. It is just like seeing the first number fit 2n, the second number fit 2n… No matter how many cases we confirm as conforming to the rule we hypothesize, we have no right to assert that the rule is necessarily correct. We experience all kinds of events with “causal connections,” but how can we guarantee that those “connections” really exist? Why could there not be some other, more complex pattern of relations lurking behind them, or perhaps sheer coincidence with no connection at all?
Radical skepticism is impossible to refute. But skepticism has not brought down the edifice of science. The foundations of science are built upon a series of “beliefs,” such as the belief that nature is “law-governed,” that causality exists, and so on. These beliefs are the starting point of science. That is to say, “causality” — more precisely, the connectedness between events — is not a conclusion of science, but one of science’s premises! It is similar to the “law of identity,” “law of non-contradiction,” and “law of excluded middle” in logic: they are not the result of logical deduction, but the premises of any deduction whatsoever. For rational people, the status of the “causality” belief seems even stronger still. If one refuses to accept the “law of excluded middle,” one can still perhaps construct a self-consistent “intuitionist logic,” but once causality is rejected, one can hardly derive anything at all.
It is worth adding that by “causality” as a necessary premise of science I mean “the connectedness between events,” that is, “the occurrence of any event is always related to other events.” This is a weaker formulation, distinct from the “principle of sufficient reason” — the “causes” of real events are often infinitely complex, and to assert that for any event A one can find an event B such that B “entails” A is highly questionable. In some scientific explanations, we try to list the entire chain of “necessary and sufficient” conditions for the event being explained; in other explanations, however, what we can do is merely show the degree of closeness of the connection between cause and effect.
So then, what is the relation between “causality” and “time”?
Clearly, our belief in causality is closely related to our sense of time; people always tend to think that the “cause” precedes the “effect.” Is that really so?
In everyday language, the temporal order of cause and effect is not strictly observed. For example: “You must not have studied seriously, because you can’t answer such a simple question!” However, when we state the meaning of this sentence more rigorously, what it actually expresses is: “Because you can’t answer such a simple question, I conclude that you must not have studied seriously.” That is to say, if being unable to answer the question is taken as the “cause,” then the “effect” is still the event that follows it, namely “my concluding,” and what “I” truly believe is still: “Because you did not study seriously, you cannot answer this question.”
In any case, people always call the earlier event the “cause” and the later event the “effect.” Even Aristotle’s so-called “final cause” does not actually reverse the temporal order. To say “for the sake of B, therefore A exists” does indeed seem to be explaining a past “effect” with a future “cause.” However, according to teleological thinking, the fact that a thing possesses some “potentiality toward B” is determined from the moment the thing first exists, and the rigorous formulation of “final cause” should be: “Because A has the tendency toward B, A manifests itself in such-and-such a way.” — still using what is earlier in time to explain what is later in time!
Of course, if time could be reversed — more precisely, if information could flow in the direction opposite to the passage of time — for example, if there were wizards who could foresee the future (not merely “predict” by means of some present signs, but directly read information from the future), or even if people from the future returned to the present in time machines to affect events in this world. In that case, only would the connection between causal order and temporal order be thoroughly disordered!
Is that possible? I dare not say. Some physicists argue that even if just a little something passed through a time tunnel, it would cause the collapse of the entire universe; other physicists argue that it may still be possible, in some way, to ensure that time travel does not result in a world absurd beyond all measure — there must be some rational events that occur to prevent anyone from going back in time to kill his own grandmother. But in any case, this is not an easy thing to imagine.
In fact, the link between causality and the arrow of time is so close that we cannot help suspecting that they are one and the same thing!
Kant regarded time as “transcendental,” a “form of intuition,” while counting comes from the a priori “sense of time” in our minds — just as geometry comes from the a priori sense of space. Perhaps it would be more appropriate to say the reverse: our “sense of time” comes precisely from “counting.” In fact, our current definition of time units is exactly 1 second = 9,192,631,770 vibrations of a cesium atom! And ancient units of time were also defined by counting some cycle of the earth or moon. Time itself is simply “counted out.” When we compare the speed of time, we must be comparing some two kinds of events — for example, if I say, “It took me a whole day to write this article,” what I am actually saying is that writing this article is connected with one cycle of day and night.
The measurement of time comes from comparisons between events; what about the “direction” of time? Although many people doubt whether time “really” has a direction, we do feel that time has a direction — that much is beyond doubt.
What determines the direction of the arrow of time? Modern physics offers a dozen candidate answers — the “entropy” direction, the expansion direction of the universe, gravity, the time-reversal asymmetry of strange particles (such as K mesons), the time-reversal asymmetry of neutron spin and its “electric dipole moment,” and so on.[①]
I am not capable of engaging in a physical inquiry into the nature of time, but the issue we are discussing is not the essence of time, but rather “what is the source of our sense of the direction of time?”
Under what circumstances would we declare that a time machine had been completed? What do we mean by “time reversal”? Obviously, we do not mean reversing the direction of entropy increase, because we can easily make an open system develop toward order, but we would not call that time travel. When we speak of time reversal, what we mean in fact is precisely the reversal of causality. Once the “future” as the result of the “present” turns back to become the cause of the “present,” once the chain of events linking cause and effect reverses into a “circle,” then we say: time reversal has occurred! That is to say, generally speaking, the direction of our sense of time is precisely the direction of causality, unless something abnormal has gone wrong in this world. Causality is exactly the source of people’s sense of the direction of time in their minds; in fact, this is precisely Kant’s claim — “The direction of time is made possible on the basis of the irreversibility and asymmetry of causal relations. Due to the philosopher of science Hans Reichenbach, this explanation of Kant’s has become the precursor of contemporary theories of causal time.”[②]
Time reversal means that causality is broken. The question is: is this possible?
Intuitively, the main paradox brought about by time reversal involves the topic of “free will” — once we can return to the past, or at least obtain information from the future, for example if I foresee that tomorrow morning I will eat an egg, but since I already know it in advance, I can perfectly well choose not to eat an egg, or to eat two eggs. Who can stop my choice? If I may choose otherwise, then what I “foreknew” before was not the “future.” But if what we foreknow is the true future, and not another parallel world, then what force will prevent me from choosing not to eat the egg? There is little point in wasting mental energy on these paradoxes, because the paradox has already told us plainly enough: time reversal is impossible. Even if it were possible, it would certainly occur in an absurdly bizarre, unimaginably way. Let these questions be left to science-fiction writers’ fanciful imaginations.
2.Determinism, fate, free will
What truly gives rise to the puzzle of “free will” is “determinism.” Newtonian mechanics foretells that everything in the world follows the same natural laws: whether stars, plants, or the human brain, all are governed by the same set of simple laws. Once the initial conditions are fixed, everything can be calculated……
As science has developed, modern scientists are for the most part much more modest than Laplace; they admit that even if all conditions are given, human beings still cannot “calculate” the future. In fact, Newtonian mechanics is only suitable for precisely calculating two-body motion; once one is faced with a three-body system that looks only a little more complicated than two-body motion, everything becomes a mess!
However, saying that we cannot calculate the future does not mean that the future is not determined. The assertion that “all the details of the entire universe were determined at the very beginning” has not been overturned. The most important belief classical mechanics brought us is this: all the rich and varied things in the world seem to require only a very small number of extremely simple formulas to explain. Diversity and randomness seem to be nothing but some sort of “illusion” and “misperception.” For example, the string of numbers “4233108251307……” looks completely random, but in fact it is just the decimal part of “π－ｅ.” We seem to have reason to believe that, in essence, everything is as simple as the collision of two balls, including human beings!
Determinism leads to fatalism — my birth, aging, illness, and death, all the events I will experience in my life, including the fact that I am currently thinking about determinism, were all settled at the universe’s very first moment!
“If that is so, then if I commit a crime, that too was already decided long ago. Why should I be responsible for the Big Bang? Therefore, I do not need to be responsible for my crime!” — This sort of sophistry does not hold, because I can also say: the trial and punishment of criminals were also already decided back then; whoever should go to prison still has to go to prison!
The key point is that fatalism damages human dignity; people are unwilling to accept it. This is an emotional issue.
The randomness introduced by quantum mechanics broke the mechanical determinism of classical mechanics. However, is quantum mechanics really the “savior” of free will?
Schrödinger declared: “Quantum physics has no connection whatsoever with the problem of free will. If there is such a problem as free will, then the latest developments in physics would not promote it in the slightest.”[③] Schrödinger was right. In fact, being wholly subject to chance is no better than being wholly subject to necessity. In the latter case, at least one can still ensure that one’s control over one’s own thoughts and body is reliable; whereas when everything becomes a matter of probability, free will seems to lack any reliable guarantee even more! To be subject to nature’s pull is still the same whether that pull has a fixed and unwavering direction or whether it is decided by dice where to drag you. The latter does not seem any more pleasant!
So, does free will actually exist? Just like the most thoroughgoing skeptic, the most thoroughgoing fatalist is equally impossible to refute! Let us take another look at Kant’s solution:
For Kant, “freedom” is also transcendental. It not only cannot be inferred in pure reason, but unlike a priori categories such as space-time and causality, it does not even play an important role in pure reason; “freedom” is of no consequence in pure reason. Yet “freedom” is the first postulate of practical reason! “In the Critique of Practical Reason, Kant says that we are constrained by the moral law, therefore we must regard ourselves as free, but we cannot know that we are free. Although a person must regard himself as governed by causal law in nature, morality and action also require us to regard ourselves as beings whose existence as noumena is not constrained by causal law; this is called the first postulate of practical reason.”[④] This postulate is crucial and differs in status from the second and third postulates (immortality and God): “freedom” is the direct foundation of practical reason. In order to ensure that our conduct is rational, we must believe in freedom.
Kant seems, at first glance, to be a lazy person: whatever cannot be explained clearly — causality, free will, and so on — he simply reduces to the “transcendental” or to “belief.” However, Kant’s approach was the result of careful thought; he quite appropriately reversed certain things that cannot be argued for by reason into the premises of reason. This is precisely the subtlety of what Kant called the “Copernican revolution”! If we keep entangling ourselves in questions such as “what is causality” and “what is freedom,” we will get nowhere! Kant modestly acknowledged the intrinsic limits of human cognition and steered clear of these swamps that would otherwise engulf us.
Deny causality, and scientific knowledge becomes hard to establish; deny free will, and practical reason becomes hard to establish. We may perfectly well deny them, but if we do, then we will be unable to think rationally or act rationally.
3.Premonition and the scientific explanation of coincidence
“Premonition,” unlike a time machine that transmits information backward in time, is not rare. Not only may the protagonists in films possess exaggerated premonitory powers; each of us in life probably also encounters, to a greater or lesser extent, some phenomena of “premonition,” such as “speak of the devil.” Under normal circumstances, we explain this as “coincidence.”
However, for example in the situation shown in films — each isolated event can be regarded as a coincidence, but when a chain of “coincidences” occurs one after another, it becomes hard to be convincing if one still explains them by “coincidence.” So under what conditions, and to what extent, can “coincidence” be used as a “scientific explanation”?
First of all, scientific explanation has a principle of “parsimony,” more or less the so-called “Ockham’s razor” principle — “Do not multiply entities beyond necessity.” For example, if I win the first prize in a lottery, I can attribute the cause to “luck,” or I can attribute it to the blessing of my great-great-grandfather’s spirit in heaven. If I want the latter explanation to be convincing, I need to additionally construct a whole series of things that have no general acceptance, such as souls and heaven, and then I must explain to people the reasonableness of those things; whereas if I adopt the former explanation, at most I need to touch slightly on some statistical language without needing any further questionable assumptions. Clearly, the former explanation is easier to make convincing.
For most seemingly miraculous coincidences, there is no need to resort to explanations outside statistics, much less to take refuge in supernatural forces. For example, in the history of the British lottery, from the 101st draw through the 165th draw, the number “15” never appeared once![⑤] Does this mean the British lottery drawings were cheating? Or that some supernatural force was intervening? Or that the number 15 has some special property? — None of the above. In fact, the probability that a specific number does not appear for 50 consecutive draws is only 0.0015%, yet the probability that there exists a number that does not appear for 50 consecutive draws rises to 7%; if one considers hundreds of draws and asks whether there exists a 50-draw span in which some number does not appear consecutively, the odds would be much higher. One could even say: in a few hundred drawings, if one cannot find several numbers with similarly unusual behavior, that would be the strange thing!
Many real-life “prophets” and “fortune-tellers” often make amazingly accurate predictions, while also making a great many wrong ones. For most of them, it is not difficult to explain the matter with statistical knowledge.
“If someone told us that an astrologer had successfully predicted earthquakes that occurred on certain days, it would certainly surprise some people, and it would also inspire others to think that he really was a person of prophetic genius. If someone told us that, in the three years 1994, 1995, and 1996, among the 169 earthquake days he had predicted, only 33 actually matched the facts, then we would begin to regard his predictions with awe. Is this reasonable? Has it been specially verified? If we consider only high-magnitude earthquakes equivalent to magnitude 6.5, that is, earthquakes capable of causing casualties and serious property damage, we find that there were 196 earthquakes in the period from 1994 to 1996.”[⑥]
By calculation, among 196 earthquakes over a total of 1,096 days in three years, the probability of having at least 33 successes in one’s 169 predictions is about 30.5%. That probability is not low at all; moreover, if we also consider more fortune-tellers, and if among them we cannot find several who predict with great precision, that would instead be strange. But only the fortune-tellings that turn out accurate will attract attention, while the many, many erroneous predictions are very easily ignored or forgotten.
We sometimes hear bad news about relatives or friends; we also sometimes suddenly think of someone, or suddenly feel a wave of unexplained irritability and unease, or are awakened by a bizarre nightmare. Generally speaking, these fluctuations of emotion are quickly forgotten. However, once, while we are feeling inexplicably irritable, we immediately receive bad news about a relative or friend, then the earlier irritability seems to acquire a special meaning. We naturally take that to be some kind of “premonition.”
Yet suppose that, on average, we have ten nightmares a year, and at the same time receive roughly five pieces of bad news about relatives or friends; then what is the probability that at least one day will see bad news following a nightmare? About 13%! Perhaps the actual probability is somewhat larger or somewhat smaller, but in any case it is not so small as to be inconceivable. It can be said that the coincidence of nightmares and bad news is not at all an unusual matter; in a group of people, or in a single person’s lifetime, if one cannot find a few examples of “premonition,” that would instead be unusual!
Still, to casually declare that “all premonitions are coincidence” would also be irresponsible. Science values evidence; it judges whether an argument is well grounded, not whether a conclusion sounds absurd, when determining facts and fraud. The reason most non-mainstream theories cannot be accepted by science is that their grounds are unverifiable; the majority of their experiments, once subjected to the strict scrutiny of skeptics, inexplicably fail, while new cases often appear when the skeptics leave. But one cannot dismiss all sorts of heterodox experiments wholesale. For example, Helmut Schmidt[⑦] designed and built an “electronic random-time” generator, using the decay of atomic nuclei to control the production of random signals, to see whether subjects could predict or even influence the occurrence of the signals; and the probability of atomic decay is difficult to manipulate by human means. These experiments also drew the attention of mainstream physicists.
Even Carl Sagan, famous for popularizing science and exposing pseudoscience, out of a rigorous scientific attitude, expressed tolerance toward certain non-mainstream studies. Sagan wrote: “During the writing of this book (translator’s note: The Demon-Haunted World), there were three propositions in the field of extrasensory perception. In my view, they are worth serious investigation: (1) by independent thought, people can (barely) influence computer random-number generators; (2) people can receive thoughts or images ‘projected’ toward them under conditions of moderate sensory deprivation; (3) children sometimes speak of details from a previous life, and it is proved to be accurate, with no way of knowing it other than reincarnation. I advance these propositions not because they are likely to be reasonable (in fact I do not endorse them), but because they can serve as examples of arguments that may be true. The latter three propositions at least have some, though still questionable, experimental support. Of course, perhaps I am wrong.[⑧]”
Carl Sagan was very clear-minded—the essential difference between science and pseudoscience does not lie in whether its conclusions are bizarre, but in whether its methods and attitude are rigorous.
In addition, what is worth discussing is: what exactly is meant by “extrasensory perception,” what is “supernatural power,” and what is “paranormal ability”?
If a person does not eat for one or two days, that is nothing remarkable; not eating for three or five days is also not strange. But if an old traditional Chinese medicine doctor does not eat for 49 consecutive days, then that must be an extraordinary matter! However, that can only be called a kind of “paranormal ability,” not some “supernatural phenomenon.” Even if there is no scientific fact to support the possibility that a person could fast for such a long time, there is still no natural law that contradicts it! “Paranormal” and “supernatural” are not the same concept.
Let us now look at the topic of “premonition.” To take a step back, even if there really were people who could accurately premonish earthquakes, would that be “supernatural”? The earthquake bureau also forecasts earthquakes, and many animals also premonish earthquakes. At most one could say that that marvelous fortune-teller can sense earthquakes a little earlier and from a little farther away than the mice can—but that would still be “paranormal ability,” not “supernatural.”
At a lecture for his sixtieth birthday, when faced with an audience question asking whether extrasensory perception exists, Carl Sagan replied: “If it exists, then it must have arisen through evolution and natural selection, just like any other trait. But what do we mean by extrasensory perception? There is a freshwater fish in Africa that can generate a static electric field and thus detect prey by sensing disturbances in that field. We absolutely cannot do that. It bears no resemblance whatsoever to the various senses we possess. Would you say that this fish has extrasensory perception?” “If it really does have extrasensory perception, what is so strange about that? Does it put science in a difficulty? Or is it merely another way of perceiving the world?” “So I think that if extrasensory perception exists, then science has the chance to understand it completely.”[⑨]
What Carl Sagan meant was: there is no mysticism in science; we should believe that the objects of scientific study are all things that can be made clear! This belief does not necessarily lead to scientism, because we are not claiming that science can ultimately solve every problem. What we are saying is: we always firmly believe that the objects of scientific study are all “intelligible”! This has been one of the necessary foundations of science since ancient Greek natural philosophy.
Here we have returned to the topic at the beginning of this article: the belief in “the regularity of existence” is an important foundation of scientific activity. If one insists that the world is inscrutable, it is hard to imagine how scientific exploration could proceed. Therefore, science does not reject “paranormal ability”; however, science will necessarily reject the concept of “supernatural”! “Paranormal ability” simply refers to certain special phenomena whose operational mechanisms have not yet been satisfactorily explained. In fact, there are many marvelous phenomena in the human body that have yet to be scientifically understood—for example, the meridian theory in Chinese medicine, acupuncture treatment, and so on; modern Western medicine has not been able to explain them. But once we take certain phenomena as the object of “scientific” study, we must believe that those phenomena are “natural” and “intelligible,” and not “supernatural” or “utterly incomprehensible.” Of course, people are free to place the concept of “supernatural” in the realm of religion or witchcraft; as long as they do not claim to be acting in the name of “science,” science has no authority to impose interference. What I want to say is: “studying supernatural phenomena in the name of science” — is impossible.
March 19, 2006
[①]See [UK] Paul Davies, *About Time: Einstein’s Unfinished Revolution*, trans. Cui Cunming, Jilin People’s Publishing House, 2002
[②] [US] Garrett Thomson, *Kant*, trans. Zhao Chengwen, Teng Xiaobing, and Meng Lingpeng, Zhonghua Book Company, 2002, pp. 1–42
[③] [Austria] Erwin Schrödinger, *Nature and the Ancient Greeks*, trans. Yan Feng, Shanghai Scientific & Technical Publishers, 2002, p. 145
[④] [US] Garrett Thomson, *Kant*, trans. Zhao Chengwen, Teng Xiaobing, and Meng Lingpeng, Zhonghua Book Company, 2002, p. 103
[⑤] [UK] John Haigh, *The Mathematics of Chance*, trans. Li Daqiang, Jilin People’s Publishing House, 2001, p. 47
[⑥] [France] Georges Charpak and Henri Broch, *The Magic Hour: Scientific Explanations of Supernatural Phenomena*, trans. Tang Zhen, Zhejiang People’s Publishing House, 2004, pp. 88–89
[⑦]See [UK] I. G. Guinness, *Mental Science: Modern Western Parapsychology*, trans. Zhang Yanyun, reviewed by Teng Shouyao and Fu Zhiqiang, Liaoning People’s Publishing House, 1988, pp. 204 and 221
[⑧] [US] Carl Sagan, *The Demon-Haunted World: Science as a Candle in the Dark*, trans. Li Daguang, Jilin People’s Publishing House, 1998, p. 340
[⑨] Edited by Yevante Tejian and Elizabeth Bilson, *Carl Sagan’s Universe: From Planetary Exploration to Science Education*, Shanghai Science and Technology Education Press, 2000, p. 186
Latest Comments
- yxy
2006-06-18 21:31:47 http://yangxinyu.blogchina.com
Imagination still needs to be expanded.
Why can there not be phenomena that are completely indeterminate? No regularity can explain them, not even probabilistic regularity.
Yet they can change according to human will.
The study of paranormal abilities at Fudan University back then was very good; I wonder what it is like now.
Translated from the Chinese original with AI assistance. The original text is authoritative.
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