Updated 13 October 2014
This lightning tour of how we understand reality is much updated and tidied from the original.
Most people assume that the nature of the real world is pretty much what they see around them and things are for the most part just what they appear to be. But how do we know? In fact, might things actually be very different under the surface and what we see is just some gigantic illusion? Let's stop and think for a moment about how our minds work.
It seems trivial to state that we can perceive only what our senses tell us. For example, we can perceive visible light but not radio waves or ultra-violet. Some aspects of reality we cannot perceive directly at all, such as electric charge or neutrinos.
Our brains then use what little sense data we do gather to build up useful models of the world. These models and the ability to build them have evolved through natural selection to help us survive, they have in themselves no other purpose. Some creatures can directly perceive magnetic and electric fields, or the polarisation of light, they must build very different ideas about what is around them, living in a different world from ours.
The associated brain activity can be broken into two stages:
First, the raw data is processed by more or less 'hardwired' circuitry. For example, simultaneous red and blue signals from our eyes are converted into a 'violet' perception, so that we perceive something which our senses never did pick up. Or, the various frequency-sensitive hairs in the inner ear produce signals, one for each frequency to which that hair is sensitive, and these are combined to produce, say a violin note. But all this is not wholly reliable and our senses can deceive us. There are many well-known optical illusions, while a surround-sound system can fool us into 'hearing' the note coming from any point in a 3-D sound stage, even though it is really coming from just a few speakers.
Then, our brains use the processed, and by now frankly unreliable, data to build and maintain a functional model of the world. It is this model which fills out conscious minds and we actually record in our memories. Unfortunately, whether or how it actually matches what is "really" going on is, by now, not at all obvious.
The Greek philosopher Socrates' favourite party trick, when buttonholed by some self-opinionated boor, was to ask him how come he was so sure of his facts. Socrates would then proceed to shred the boor's arguments and use them to prove that nobody could know anything for sure. The finale was to point out that he, Socrates, knew more than the boor because he at least knew that he knew nothing else.
Some people believe that, because we can know nothing about any 'underlying reality' behind the world of our senses, we therefore have no evidence that such a reality exists. Therefore it doesn't. In the so-called "Copenhagen interpretation" of quantum mechanics, only the start and end of an experiment are real and what happens in between is of no concern: it is enough that the maths can link the start and end. Many people prefer to believe that although we can know nothing about the 'ultimate reality', there must obviously be one or we wouldn't be here to be confused about it.
Some regard this apparent inaccessibility as a carte blanche to fill the gap with whatever reality and truth you want to create for yourself.
Some others take a marginally less drastic liberty and believe that, because perceived reality is the only reality than a conscious mind can ever establish, the underlying reality can exist only because there is a God who continually perceives it. This is actually a more sophisticated view because it both recognises the subjective nature of our own human models of reality while at the same time demanding a deeper reality to underpin them. The need for an observer to 'collapse the wave function', and thus actively create the outcome of a quantum mechanical experiment, has latterly been offered as support for this view. However, quite why God should choose to first create and then collapse His own wave functions is not explained.
The idea that God dreams it up merely replaces the puzzle of underlying reality with the puzzle of God's reality and is no help at all. The Buddha understood that the only reality we can normally grasp is perceived reality, i.e. illusion, but he also believed that when he discovered the meditative state he called Nirvana or enlightenment, then he directly experienced the ultimate reality of existence. However he also said that this experience cannot, unfortunately, be described in words. Taoism too teaches the illusory nature of the mind and posits an underlying "Tao" which is the source of all things. The aim of the Taoist sage is to dissolve one's sense of self and become one with the Tao. Unless you become one of those rare enlightened ones, you can never know the truth. Since then another meditative state beyond Nirvana, called Nibbana, has been discovered and modern neuroscience makes it hard to maintain that either Nirvana or Nibbana is more than just another kind of illusion.
Some people believe that we can indirectly learn something about the true reality by studying the nature of perceived reality, which is 'overlaid' onto the true one. The main tool for doing this is the 'scientific method' of observing, forming models, testing the models in experiments, observing the results ... and round and round, learning more each time.
Some believe in revealed truth, e.g. most religions. Their justifications for the source authority invariably come from the authority itself - 'Believe in me because I tell you I'm right'. But do not dismiss them because of their circular reasoning: if the authority itself were actually the true 'underlying reality' we seek, its justification would indeed be self-evident. Consider the teachings of say Buddhism or Taoism from this point of view. Consider also the attitude of some scientists - 'Believe in science because scientific reasoning tells you it's right.' If some respected physicist evangelises a new idea, say multiple universes or eleven-dimensional spacetime, it can be hard to decide which aspects are rational and which arbitrarily revealed by an overactive imagination.
Indeed, the parallels between Eastern religious philosophy and quantum mechanics are striking and have been well documented by authors such as Fritjof Capra. Taoism and Buddhism both embody much the same principles and have long bickered over who thought of which teachings first. Much has also found its way into or sometimes from various branches of what we now call Hinduism. It is perhaps surprising to the average Westerner that many of these concepts and insights, developed over 2,500 years ago, are more helpful than our own traditions in understanding the reality behind quantum mechanics.
In the end, the belief system that any one person adopts depends on the particular flaws in the mental model of the world which they grew up with. Indeed, any such belief system is itself one of the flaws. Thus, different viewpoints have differing values for different people. The best viewpoint is one which enables you to move on to a less flawed viewpoint, and so on.... Reminiscent both of the historical progress of science and of the Buddhist path to enlightenment. The endpoint of this process is not yet in sight, in fact opinions differ as to whether there actually is one or whether we might be capable of reaching it anyway.
His Holiness the 14th Dalai Lama has said that, "If science proves some belief of Buddhism wrong, then Buddhism will have to change." I'll buy that.
Science's best shot at understanding the world is currently quantum mechanics. But that is just a bucketful of equations, with some rules on how to use them to predict the results of your experiments. The underlying reality, what all those mathematical symbols actually mean, why one equation works better than another, and what happens when you are not busy measuring something, remains obscure. The study of this reality may be called quantum philosophy.
We know a few things about quantum reality, chiefly that it is so utterly weird and counter-intuitive that anybody who claims to understand it has, by that simple claim, pretty much proved that they don't. We know that it is "non-local", that the "spooky action-at-a-distance" so disliked by Einstein is in fact embodied in its very fabric. And we know that a cookie can exist in multiple simultaneous states of fracture until it decides which way it is going to crumble. OK, that's probably a metaphor, real cookies may be too big for that to happen - but hey, we don't even know if it is just a metaphor or the real deal!
Speculations as to what may lie "down there" are many, and the better ones all carry the hallmark of weirdness. Stick too close to what your flawed brain is telling you is common sense, and your theory will embody those flaws. The weirdness simply cannot be explained away by "it's just common sense particles with a bit of hand-waving", or "it's all in the mind of the observer". No, the truth, whatever it may be, is far weirder than such simple-minded ideas.
But there is weirdness and then there is true insanity, what has been called the Monty Python test. Everett's many-worlds theory says that every time something happens new universes are created. Say there are two possibilities for an electron to have an up or down spin. When we measure it, each possibility splits off to happen in its own newly-created universe. The scientist sees one particular outcome because they happen to be in the particular universe it happened in, elsewhere there is a parallel scientist who measured the opposite result. This elegantly resolves a mathematical niggle with all those equations and the theory has gained some followers. But let's just push it a little further. Take some photon of light from a star. It travels for perhaps ten minutes or ten million years, who knows. Then it strikes some rock somewhere and the rock heats up ever so slightly. Are we seriously to believe that, with I don't know, say ten billion billion billion rocks out there, the universe suddenly splits into ten billion billion billion copies of itself, each with a different rock slightly warmer than the others but otherwise identical? What about all the other gazillions of photons being poured into space every second of every day? It would mean more universes popping fully-formed out of nowhere every day than there are atoms in any one of those universes. I don't care how neat the maths might be, for me this blatantly fails the Monty Python test. Everett later modified his ideas to allow at least some of these multiplying universes to collapse back down into each other again, but that was really just a technicality and the true insanity remains.
A viable theory of quantum reality must tread that clouded path which lies somewhere between the depths of common sense and the heights of utter madness.
The history of science charts the relentless discovery of new, hitherto unsuspected areas of reality, brought about by the invention of new instruments. The vast emptiness of space was discovered by the telescope, electromagnetism was discovered using wire coils and spark gaps, the vast world of molten rock beneath our feet was discovered using microscopes, test tubes and seismographs, atomic structure was discovered using radiation sources and photographic plates or Geiger counters, and so on. What areas of reality lie unsuspected to this day because we have not yet dreamed up the instruments to detect them?
A lot of quantum scientists think that philosophy is easy and they are pretty good at it. It isn't and mostly they aren't. A lot of philosophers think that science is easy enough to understand and they are pretty good at understanding it. It isn't and mostly they aren't. Both disciplines are actually quite hard and need a lot of solid education and practice before you are going to learn to tread that narrow path between the naive and the insane. (I can't pretend to have got there yet myself but, like Socrates, I am at least aware of my ignorance.)
Our brains did not evolve to solve the problems of the universe, or even to think rationally, they evolved in order to survive and breed. In biological terms we are nothing more than an organism whose DNA evolved to fit it better in a niche where some kind of capacity for thought turned out to be better than none. As our brains evolved capabilities that fitted us better and better to exploit the niche we found ourselves in, thought was just a byproduct of that DNA-driven selection process. Whether any of that thought might be rational depends solely on whether that rationality helps our selfish genes survive and multiply.
The general problem we face in figuring all this through is: given that our brains evolved their ability to build models of reality for one narrow purpose using only unreliable interpretations of incomplete data, what can we actually find out about the underlying reality? Clearly, such a mental model of reality is likely to be deeply flawed. Our model includes many sub-models, including models of things such as 'self', 'truth' and 'reason'. What makes any progress at all so tricky is that we are forced to use the flawed models to study their own flaws. A scientist basing his ideas on cheap philosophy, or a philosopher doing the same with cheap science, are excellent examples of this.
This problem of 'thinking about thinking' is made even trickier by the nature of language, which is not only somewhat less effective at sharing ideas than telepathy but is also integral to these kinds of thought processes, and often leaves open ambiguities or makes hidden assumptions. For example I have throughout been assuming a conventional material world that is feeding our senses, though I have never actually said so until now. I have to make that assumption to at least some extent, even when discussing whether or not such a world exists, because that is how the English language is built. Mathematics too is a language of it own kind, and the same issues arise here. Every mathematician knows that complex proofs are always plagued by hidden assumptions, which must be ruthlessly weeded out.
1. Set out your Assumptions. 2. Proceed through a rigorously reasoned Argument... 3. ... until you reach one or more Conclusions.
This sequence, assumptions-argument-conclusions, is absolutely fundamental. It defines the logical process which underpins all of rational thought.
But it has some interesting consequences.
It is very general. There are many distinct systems of logic, each comprising a unique set of assumptions. Any one such system will form a big part of your own assumptions. (the remaining assumptions define the topic under investigation). Philosophers spent many years trying to find a system which is both consistent and complete, so that it could be applied rigorously to the scientific method. If your assumptions are inconsistent, it turns out that you can prove anything at all, and even reach directly contradictory conclusions. If your assumptions are incomplete, you may be unable to reach any conclusion at all.
Many assumptions turn out not to be independent, but to be based on deeper assumptions and not really to be assumptions at all. Others seem to be interdependent in ways which are not obvious: two apparently different sets of assumptions can end up giving identical results, effectively making them two different expressions of the same logical system. The sets taken as sets are logically equivalent but the individual assumptions within each set are not. Have we necessarily missed a trick and included assumptions which can be broken down further into more fundamental ones, or is the nature of logic really like that? Last I looked, this was an unresolved problem.
How do we prove that the only reality worth seriously considering is scientific reality? Since this idea cannot be tested scientifically without first assuming it is valid, is it not pointless philosophical speculation? How can we even be sure that the three-stage logical process is the only one that works? Isn't that three-stage process in itself just one of our assumptions? Might there be other kinds of reasoning that are equally valid? How can we be sure there aren't? If you can't reason rationally until you have a starting point, then how can you reason out a rational starting point?
Much agony has been exercised in seeking answers to this kind of fundamental question. We have found a surprising number of assumptions about things buried in our customary habits of logic, and dropping some of these assumptions has created whole new mathematical and philosophical disciplines.Ultimately, we cannot prove that the fundamental starting points we have discovered are actually the right ones.
Logical positivism was one brave attempt. It takes its guiding principle to be that "No statement has any meaning unless it can, in theory at least, be verified". This is called the verification principle. Thus the statement that "The Earth is 93,000,000 miles from the Sun" is verifiable, so it has meaning. But the statement that "God lives in Heaven" is not verifiable, so it is meaningless to a logical positivist. But consider: the verification principle is itself a statement. It can therefore only have meaning if it is verifiable. How do you verify the verification principle? In short, you can't. Positivists hate to be reminded, but positivism rests on a leap of faith just like any other creed.The best we can do is to try and do better than last time. Mathematicians work in exactly this way. For a beautiful and accessible account of this I can heartily recommend a book by Imre Lakatos. Do not be put off by the title, it is very readable and comprises a set of dialogues between a school class and their teacher. The book is called Proof and Refutations. There, you would never have given that title a second glance if I hadn't told you how harmless it really is inside, would you?
The tenacious logician might now ask, "But how do we know that this endless cycle does actually get better? Might we not be digging ourselves deeper into a hole without knowing it?" Well of course, technically we might. Here, the Buddha had a piece of advice for his more sceptical companions: "That's fine, you don't need to believe me if you don't want to, but look, what choice have you got?" Some things, two and a half thousand years cannot improve on.
When all this logic is applied to understanding the world around us we call it the scientific method, often summarised as a repeating cycle of "model-predict-measure". The scientist comes up with a theory, uses it to predict something, then sets up an experiment to measure that something and see if they got it right. No? Then come up with an improved theory and try again. Just keep trying to do better each time round. Fundamentally, all of quantum mechanics, relativity and the rest are developed by this method, and this method alone.
Any scientist who thinks he is being 'logical' may well be so. But it isn't going to get him very far in 'proving' anything about the real world, he can only prove things based on his assumptions. All that we can do is to keep working downwards towards rock bottom. Of the assumptions which prove truly fundamental, which ones we keep and which we drop becomes, intellectually, a matter of choice. But some seem to do better than others in explaining the way the world works.
Ultimately we are thrown back on the Monty Python test: a malignant demon or a master computer that creates every illusion directly in my mind? A gazillion Universes spawning every nanosecond to cover every possible outcome of every single quantum interaction? A pantheon of perfidious, bickering Gods and Demi-Gods and Spirits eternally acting all too humanly? The world created a few thousand years ago by a God Who chose to bamboozle us with a faked geological and evolutionary past in order to "test our faith"? All fail the test, they are all frankly very silly indeed.
The interesting thing about the Monty Python test is that it is a blend of intuition and reason. Cold reason admits a technical possibility, intuition evaluates that possibility as not merely remote but positively absurd. Indeed, that absurdity test lies at the heart of any attempt to apply reason to the real world. And different people have different intuitions, for example Everett had the opposite intuition about multiple universes from mine. We are back to the way the brain has evolved, with respect for neither useless fantasy nor cold logic but merely for seeing tomorrow's dawn, wherever one happens to be. Can we trust one of the key characteristics of our faulty thinking machine to justify one of the key characteristics of the way we analyse reality? Do we have a choice?