Updated 2 May 1999
This comprehensive lightning tour of, erm... reality is an edited and slightly extended compilation of postings from a newsgroup thread on an intranet somewhere out there ....
Rather than cover the whole field, which would probably take an entire philosophy library, I will stick to my own view. Others will no doubt add their two penn'orth as we go.
Do bear in mind that, due to the nature of language and the problems of 'thinking about thinking', I have to assume a conventional material world, as a linguistic device, even when discussing whether or not such a world exists or what it is like (Pedanitc nit-pickers please note).
Let's start with a theory of how we see reality. It seems trivial to state that we can perceive only what our senses tell us. For example, we can perceive '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 this sense data to build up helpful models of the world, to help us survive in it. But note that this is a two-stage process:
First, the raw data is processed by 'hardwired' circuitry. For example, simultaneous red and green signals from our eyes are converted into a 'yellow' perception, so that we percieve something which our senses never did pick up. Or, signals from the various frequency-sensitive hairs in the inner ear are combined to produce, say a violin note: a stereo sound system can fool us into 'hearing' the note coming from a point on a 3-D sound stage, even though it is really coming from the speakers on either side.
Then, our 'minds' use the processed, and by now unreliable, data to build the functional model of the world. This model includes many sub-models, including models of 'self', 'truth' and 'reason'.
The general problem we face is: given that we build our models on unreliable interpretations of incomplete data, what can we find out about the underlying reality? The reason that this is so tricky is that we are using the flawed models to study their own flaws.
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. Needless to say, when he pulled this trick on the leading gentlemen of Athenian society, and also refused to sleep with them, they engineered his suicide (ooh, get you, you bitch!).
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.
Some take this a step further and believe that, because percieved reality is the only reality, the underlying reality exists only because God continually percieves it. 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.
Some 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. The Buddha said that the only reality is percieved reality, i.e. illusion - we can know nothing of the ultimate truth unless we achieve Nirvana, which is a state of direct experience of the truth (and cannot, unfortunately, be described in words).
Some believe that we can learn something about the true reality by studying the nature of percieved 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 is itself the true 'underlying reality' we seek, its justification is indeed self-evident. Consider the Buddha's teachings from this point of view. Consider also the attitude of some scientists - 'Believe in science because scientific reasoning tells you it's right.'
Where do I stand? Well, I suspect that the viewpoint, or belief system, one adopts depends on the flaws in the mental model of the world which one grew up with (see above). 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. So am I a Buddhist, then? Well, I cannot (yet?) accept the doctrine of karma and rebirth and so on which underlies all his ideas, so no, not really. But I do find that many of the concepts and insights developed over 2,500 years ago are helpful in understanding the reality behind quantum mechanics. And to paraphrase the Buddha; 'have you got a better idea? No? Then you might as well follow the path until you have'.
There was a young man who said "God
Must find it exceedingly odd
To note that this tree
Just ceases to be
When there's no-one around in the quad."
"Dear Sir, Your query is odd.
I am always about in the quad,
And therefore this tree
Will continue to be,
Since it's observed by, Yours faithfully, God."
A philosopher, one Bishop Berkeley,
Remarked, metaphysically, darkly
"Quite half that we see
Cannot possibly be
And the rest's altogether unlarkly"
There once was a fellow named Peel,
Who said "Although pain isn't real:
When I sit on a pin
And it punctures my skin,
I dislike what I fancy I feel."
Dave wrote, "I think the only reality worth considering seriously is quantum reality, since it can be predicted measured and tested. Especially what Bell's theorem tells you about it. Any other kind is open to philosophical speculation which gets you nowhere."
To which Mike replied, "What about the reality of the idea that the only reality worth considering seriously is quantum reality? Since this idea cannot be measured or tested, it must, by your reasoning, be pointless philosophical speculation."
Postscript. 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, atomic structure was discovered using alpha rays, and so on. What areas of reality lie unsuspected to this day because we have not yet dreamed up the instruments to detect them?
Dave and Mike lead neatly on to my next topic: logic.
Any logical process can be broken down into three elements:
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.
But it has some interesting consequences.
There are many systems of logic, each comprising a set of Axioms. Any one such system will form a big part of your assumptions. (the remaining assumptions define the topic under investigation). Philosophers spent 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.
Enter Godel's Incompleteness Theorem, which shows that in any logical system which is both consistent and complete, it is possible to make statements (e.g. about the real world) which cannot be evaluated within that logical system. The statement, 'This statement is untrue', is the classic example. To resolve such statements, the logical system must be expaned with new axcioms. However, the same problem arises in the expanded system, necessitating more axioms, and so on. Thus, no defined logical system can cope with all possible statements about the world. Thus, by virtue of being a defined logical system, science cannot tell us everything - it has blind spots.
Consider now the process of deciding on the rules for 'scientific reasoning'. We must choose a set of axioms which are complete, consistent, and yield sensible conclusions when applied to scientific problems. What axioms shall we choose? Note that we cannot use scientific reasoning to choose our axioms, because we haven't defined 'scientfic reasoning' yet. Let us appeal to 'logical reasoning'. The same problem applies - how do we choose the axioms for logical reasoning? Can we appeal to mathematical logic? No. mathematics alone does not tell us how to apply it to the real world.
We are forced back onto intuition and 'common sense'. Fundamentally, all the axioms of quantum mechanics, relativity and the rest are all chosen 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. To recap: the whole edifice is built on intuition, and there are still no-go areas it can say nothing about.
Guy (above): "Philosophers spent years trying to find a system which is both consistent and complete, so that it could be applied rigorously to the scientific method."
Dave: "The scientific method works pretty well. There's no need for any input from philosophers."
Guy (above): "By virtue of being a defined logical system, science cannot tell us everything - it has blind spots."
Dave: "But what is a defined logical system? Science doesn't proceed by axioms. Some theories like special relativity were, but in general they don't. Its the old model, predict, measure."
Guy: "You sound like a positivist. Let me explain the logical variety first:
"Logical positivism 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 'The Earth is 93,000,000 miles from the Sun' is verifiable, so it has meaning. But the statement '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. Positivism rests on a leap of faith, like any other creed.
"The whole edifice of the scientific method rests on similar grounds. To say 'The scientific method works pretty well' begs the question, by whose lights? By the lights of the scientific method? Once you get wrapped up in such a cosy little world, you can never tell when something unknown is creeping up on you ... "
Guy (above): "We are forced back onto intuition and 'common sense'. Fundamentally, all the axioms of quantum mechanics, relativity and the rest are all chosen by this method, and this method alone."
Dave: "Not really. While people are doing the first bit of creative research they need physical intuition to find a new model or paradigm. But you can't choose anything as if you were writing a novel. It has to fit in with the rest of science."
Guy: "You are missing the point. The 'rest of science' is justified according to everyone's intuition that it is a 'sensible' model. There can be no ultimte proof of this. Witness Einstein's demolition of Newton's 'sensible' law of gravity, or deBroglie's demolition of the 'sensible' particle theory of matter."
Guy (above): "To recap: the whole edifice is built on intuition, and there are still no-go areas it can say nothing about."
Dave: "Can you give an example of some area of knowledge which couldn't be investigated by the scientific method?"
Guy's list:
Theology - The nature of 'God' or the 'Afterlife'.
Morality - the ultimate justification of 'right' and 'wrong'.
Consciousness - not how the brain works, but why there is a 'little me',
an 'enjoyer of the self', attached to it.
The 'cause' of the origin of the Universe.
Inside a Black Hole (you can't do experiments, even in principle).
Ontology - the study of 'being', or: is reality really real?
Counterpoint is an SF short story to
get you thinking, especially about the punchline.