"Stupid question" is the average response to that query. I suppose you're going to start on about the table disappearing from in front of you and stuff like that now. Er... not exactly. Lets take a trip.

You are on a sandy beach blissfully sunning yourself. (Or, if you're like some of us wary types, you're hiding in the shade somewhere having become paranoid about skin cancer.) You can hear the gentle crashing of the waves on the nearby shore. You can smell the salt. You feel the heat. Shade or sun, its warm enough for you to be wearing a swim suit just within the bounds of early 21st conventions on decency. Beneath your beach blanket you are aware of the accommodating contour hugging of the fine sand.

Suddenly the idyllic afternoon is shattered. The beach wally turns up. Nowadays, of course, this usually means the antisocial nerd with a ghetto-blaster who parks himself 30 feet upwind and shares his love of obscure imported reggae or mind numbing heavy metal with the rest of the known universe. However, this is 50 years hence; things have moved on. His latest toy is a "Virtual Reality Sensory Transmitter" capable of transmitting apparently authentic signals direct to the optic nerves bypassing the retina of your eye. He tunes it with the usual gay abandon, and you suddenly realise that instead of a sandy beach, you can now see snow as far as the eye can see. You know what's going on, of course, you've had this trouble before. In any case, all other senses confirm the status quo. You can still feel the warmth of the sun, hear and smell the sea nearby and feel the warm sand under the blanket. So you merely fume awhile till the pillock focuses the toy on some other victim. You know that the best way to escape his attention is to fane complete indifference - as though you can't even perceive the machine's effects.

On your next visit to the beach (obviously having failed to find a convenient "members only" private stretch where nerds are barred) you find yourself hit by a much more advanced version now capable of transmitting appropriate signals direct to all five sensory nerve pathways. This time, without warning, you find yourself lifted up and flown at incredible speed to the Arctic tundra and dumped down on an ice floe with a polar bear. And you're still only wearing the swim suit! Its bloody freezing. The wind chill factor takes the temperature down to minus 40, The ice under your feet is excruciatingly cold and rather slippery. The bear is hungry and advancing towards you. What do you do?

Well, if you're as cool as you now feel, you just sit there and persuade yourself its another damned illusion; you're not going to let it get to you. Eventually the wazzock will get bored and pick on some other target.

But let us suppose that you've never heard of such a machine and have no reason whatsoever to suspect that such a device exists (like today - 2003 - in fact) What would you do in those circumstances? Well, if you don't faint with fear, you get up and run like hell! (or dive into the icy waters and try to swim out of danger).

Believing what you had just experienced to be real, however bizarre, you would have no choice but to act in accordance with what your senses were telling you. You wouldn't know that the sense data was entirely artificial because you would have no way - outside the senses - of confirming whether what you are perceiving actually corresponds to "reality".

Any more than you have now.

How do you know that such a device isn't controlling your sense data right now?

Of course you are psychologically certain that it isn't. But if it was any good... well, you would be wouldn't you?

Of course, if you've seen "The Matrix", this kind of illusion will be familiar territory. If you haven't seen the movie and this is a novel concept, it is not our intention to persuade you that such a machine exists, or that your current sense data is generated by it. The Universe is difficult enough to explain as things seem to be; the existence of machines like that really would be gilding the lily. Nor do we want thousands of readers wandering around doubting their own existence - it can spoil your whole day! All we want to do is get you to accept that we do not - indeed CAN not - know that it or something similar does not exist. As a consequence, we have to accept that merely perceiving something with our senses is never absolute proof of its existence. All it proves is that the perception exists.

You may be familiar with Rene Descartes journey down this road. Having rejected all sense data as unprovable he went on to conclude that the only valid starting point was "Cogito Ergo Sum" (I think therefore I am). Even this, however, is invalid. "I think therefore something is" is really as far as we can go. We can not know that the thinker is "I", even if the perception is of self. That perception, like all others, is unprovable.

So the answer to the question ("Do we Exist?") is "We don't know". However, it is important to emphasise other results of that chain of logic. We referred, for example, to the polar bear situation and what you would do about it; particularly if you had never heard of a sensory transmitter. We pointed out that in such a situation, you would have no choice but to trust your senses and act accordingly. This is valid - whether or not the sense data is artificial. We are programmed to respond to and to make judgements based on sensory stimuli. It is quite irrelevant to that programming whether the sensory data reflects reality or a fantasy world. That is why there is no intention on our part to persuade you not to respond to what you see - or even to doubt it. You don't have alternative "safer" data sources; you're stuck with it.

The vital point is to distinguish between what you believe (that what you see is real) and what you know (nothing!).

This is such an important point that, if you don't mind, we're going to repeat it.

The vital point is to distinguish between what you believe (that what you see is real) and what you know (nothing!).

The significance of the distinction is fundamental when we come to answer the second and third questions. As much as anything, this book is an attack on "authority" - by which we mean, for example, any individual or organisation which declares that it "knows" the "truth" (especially "what is best for you"). 

Now if we can't even state with logical (as opposed to psychological) certainty that we or anything else exists (other than a woolly "something") then it follows that we can say Absolutely Nothing Else with "certainty" either; not even that the best tested scientific theories accurately describe "reality".

Nevertheless, there are those who assert that  their particular Political theory or Moral Code, (all examples of  which are somewhat less rigorously tested than any scientific hypothesis) does indeed represent some fundamental Reality or Truth. Such assertions amount simultaneously to the ultimate in both intellectual arrogance and ignorance.

Unlike political theories and moral codes, Scientific Theories are generally based on large numbers of (more or less) carefully monitored observations each of which is open to the same logical challenge as all other perceptions. The best we can ever manage, therefore, is to say that the cumulative "evidence" (i.e. the data gathered and perceived by our senses) either supports or undermines the analysis of our perception of reality. And, frankly, that is perfectly adequate in our day to day affairs. Until or unless the world stops behaving in accordance with the rules we seem to have divined, then there is little point in worrying about whether those theories are, in fact, completely accurate descriptions of the world or mere imaginative constructions. All that matters is that we've done our best to explain what is going on and the explanations "work".

We believe, for example, that an electrical potential applied across a resistance will cause a current to flow in the resistor. (Don't worry, we're not about to start getting "technical") It doesn't matter too much if our understanding of this process is 100% accurate or only, say, 50%. What matters is whether or not the light comes on when we throw the switch.

What matters, much more, in our daily lives, is that, given that we have to live with this fundamental uncertainty about even the most basic questions we can ask - questions we can answer with our sight, smell, touch or whatever - we really ought to be asking how can anyone get away with making authoritative declarations about matters of mere human judgement (like the concepts of "Right and Wrong") in answering those questions relating to "how we should behave".

And if we were to ask that question, the obvious answer ought to be, simply, that "they can't" (get away with it). And the relevance of that answer is that, as we all know, the world is in fact run by people who either ignore or remain unaware of this obvious conclusion and blithely make such declarations not just once or twice in their illustrious careers but as a matter of course on a day to day basis throughout their reign. And to a greater or lesser extent, we let them.

The real damage, of course, arises from the support and encouragement they get from us lesser folk who, either more ignorant or more apathetic than our leaders, believe or accept that what we hear has some validity. This is seldom the case, as we will demonstrate from time to time. Politicians are, to a greater or lesser extent, nearly all "manipulators of the truth". That won't surprise the cynics. It may interest you, though, to see just how easily political statements fall apart under any rigorous analysis. Most are not just false, they are often literally "meaningless". However, we digress. These matters are appropriate to the Third Question, which we'll begin to deal with them more fully in chapters Six & Seven. Meanwhile, back at the First Question...

The Limitations of Perception

Lets try another angle. Everybody (well all the people we've encountered to date anyway) believes they exist and will confidently assert it. Does that help? Does it become more "probable" that we exist just because so many of us appear to believe it?

Unfortunately Not.

None of us as individuals can get past the logical barrier that all of "you" might be part of a set of artificial data. So whilst our perceptions of others like ourselves who appear to have their own set of beliefs, together with an apparent ability to behave in ways beyond our control, all combine to reassure us psychologically (and make it even more difficult for us to believe that all this is illusion) it doesn't actually eliminate the possibility of illusion. Unless we can find or offer some kind of "guarantee" that at least one or more of our perceptions COULD  NEVER BE mere illusion, then it is meaningless to discuss the probability of the rest of the picture being "real". And whether we care to admit it or not, we're ALL in exactly the same position with respect to what we believe to be the rest of the world. We all appear to share the same basic beliefs about our existance and none of us know of any logical proof that our belief is correct.

So - all it means when we say "we exist" is that we have an overwhelming conviction that we are not merely imagining everything. So overwhelming that is unlikely that anything could persuade us otherwise. Yet despite this, we are compelled to admit the logical possibility that it is all one or more dreams. 

This is the limit of perception.

It is also the limit of language. We can not formulate statements about the world which can crack this logical barrier - primarily, perhaps, because language has evolved to explain and deal with our perceptions; not to challenge them.

This is the essence of philosophical scepticism, taken to its limits by the school of philosophy which called itself the logical positivists. Fortunately, you'll be relieved to hear, we needn't stop there. Providing we accept this concept of the absolute lack of logical certainty and agree that it is only, in fact, possible to experience psychological certainty, we can go on about our normal business. In other words, we can believe many things but know none about the true nature of the universe. (except possibly that!)

It follows that our exploration of reality is governed by our psychology (what we Believe) rather than our ability to detect absolute "truth".

A trivial example: What we really mean, for instance, when we say that we "know" that "ice melts when it warms up" is as follows:

First, we believe there is a substance we call water. Second, we believe that it is liquid at "room" temperatures. Third, we believe it becomes a solid we call "ice" if the temperature of the liquid is permitted to drop below a certain point. And fourth, we believe that this solid once again becomes liquid when its temperature rises again.

All these phenomena can be witnessed through our senses and repeated at will. Hence, we have no choice but to trust those senses. We cannot conceivably design a test which could prove to us - entirely independent of our senses - that such observations were either valid or invalid. Why not? (for example using a machine which measures whether something is liquid or not) Because, even if the machine is somehow capable of making a judgement, we still have to perceive that judgement using these pitifully limited senses!

"But surely there are some well accepted absolute laws without which all science would be meaningless; take the second law of thermodynamics for instance - the Energy in a system must remain constant - (which tells us that matter and energy can not be created or destroyed, only converted). If this law was invalid, then most science would be equally invalid." - we hear you say.

First off, we are not saying that it is invalid. We are merely pointing out that it can only be said to be a successful explanation - to date at least - of what we perceive in the universe. IF that perception could ever be proved unambiguously accurate then that certainly would help the theory. But we can not  have logical certainty about the perception.

Second, in fact, no physicist worth his or her salt would dare claim this or any other law as absolute. It is merely, as we said, the most successful explanation to date. As was the Ptolemy's theory that the Earth was the centre of the Universe until Copernicus appeared. As was Newtonian mechanics before Einstein came along and so on. As it happens, there are already causes to doubt the validity of the second law which arise from some of the stranger consequences of quantum mechanics, particularly concepts such as "virtual" particles which are possibly inhabiting the vacuum of deep space. If you're into stuff like that, go read anything written by the Cambridge Physicist, Stephen Hawking, who has the gift of making the most esoteric scientific concepts comprehensible even to the layman.

Mind you, - assuming, of course, that our perceptions do bear some resemblance to reality - it has often seemed to some of us that the most obvious contradiction of the second law is that an amazing amount of matter and energy - the Universe - does exist, and may well have been, at some stage, "created". If it was, then even if that law does appear to be valid now, perhaps it hasn't always been and, by the same token, it may not always remain valid in the future. (And physicists may finally be able even to answer this fundamental question. See this story - added Feb 2007)(cached)

"OK, what about a medical example; if, for instance, doctors crack the AIDS problem and produce a cure, isn't that pretty tangible evidence of the Truth of their beliefs?"

Nope. The same proviso applies. If their initial perceptions are accurate then their deductions are probably also accurate. But we still don't know about those initial perceptions. However, what we can reemphasise, is that it doesn't matter, especially to the victims. Their perceptions are that a) they had AIDS and b) they are cured. They don't give a damn whether that is grand illusion or reality, the effect on their lives is identical. What we can also say is that the evidence (the perceived effectiveness of the cure) is tangible support for the rationality of their beliefs (as opposed to truth).

Rationality Defined

Now this word "Rational" is very important. Essentially, all our belief structures can be sustained provided they are Rational. i.e. We can go on "usefully" believing something as long as it continues to "work"; and whether it meets this criterion can, in turn, be determined by establishing whether the belief has been arrived at by following certain rules.

What do we mean by "Rational" in this context? And what are these "rules" which govern whether or not such a belief is rational? Well, you'll be relieved to hear that "Common Sense" is the answer in more ways than one. "Rationality" describes your behaviour when your beliefs or actions accord with the confirmed observations of your senses.

The "rules" are very simple. Before drawing a conclusion about what you observe, (particularly if its a new observation)

* try to figure out as many potential causes as you can, of the event being observed; and then

* try to eliminate each one of those hypothetical causes by further experiment, observation or argument from agreed principles. If, at the end of the day, you have eliminated all but one cause and are able to repeat the observation or experiment by invoking this cause (or watching it invoked) at will

* then it is reasonable - Rational - for you to believe that your explanation of what you see is a good one.

As Sherlock Holmes famously, and almost appropriately, put it: "When you have eliminated the impossible, whatever remains, however improbable, must be the truth."

This, loosely speaking, is the principle of verifiability, - the basis of "Empiricism" - which is what we will take a look at next. 

(Last Updated 20 Feb 2002)