MonoRealism Philosophy Site

Induction Rules

Philosophical Reflections XXVII

Part A: Truth & Lies

In Philosophical Reflections 25 and 26 we looked at the validity of inductive reasoning and the nature of truth. Because induction is so important in generating our knowledge, it is clearly important to understand the rules of inductive reasoning.

We have already covered some of the fundamental rules of inductive reasoning when discussing the validity of concepts (Philosophical Reflections 24) and the basis and validity of inductive reasoning (Philosophical Reflections 2526). Here we'll look at the rules of evaluating evidence. What evidence can you trust, and what can't you trust? How much weight should you put on different kinds of evidence?

We will start with general principles and move on to some specific rules.

Nature Doesn't Lie

That nature doesn't lie is inherent in reality. A is A is one expression of it: things act according to their nature and cannot act contrary to it.

Consequently facts must never be ignored. Contradictions cannot exist, so any fact of reality which conflicts with what you think you know shows a hole in your understanding. In any conflict between what you believe and reality, it is reality which you must go with. All induction is based on observed reality, therefore, observed reality cannot be ignored or evaded if you wish to enjoy a consciousness free of contradictions: and thus be free to pursue your values without being sabotaged by wilful blindness to reality. To ignore reality is to undercut induction's foundation – which is to undercut the functioning of your mind – which is to undercut your primary tool for achieving knowledge, life and happiness.

How much is adherence to reality worth? That is the same as: How much is your life and happiness worth?

Senses Can Lie

In an important sense your senses cannot lie. They are physical organs which merely act according to their nature. Thus your retina responds to light and your nerves process and transmit its output according to their biochemistry: they have no volition in what they do.

However, as is well known, sensory illusions occur both within our nervous systems (e.g. geometric optical illusions, water feeling hotter or colder depending on previous temperature exposure, and the effects of certain drugs) and externally (e.g. mirrors and mirages). This is one of the reasons why it is not mindless acceptance of sensory input which is the source of knowledge, but the application of reason to that sensory input. It is reason which tells us what is real and what is illusion: indeed, that is how we know there are illusions.

The primary rule of induction is to integrate all the evidence of all your senses, past and present, into a non-contradictory whole. Your senses always tell you something about external reality: but exactly what that something is, only reason can tell you.

Feelings Just Feel

Feelings neither lie nor tell the truth: emotions are not tools of cognition. They are value-based responses built on past experience and cognition. If your emotions are not pathological or misguided, but are rooted in integrated, rational values, then they are likely to prompt you to act appropriately to the situation. But valid emotions follow valid understanding: they are not evidence of validity in themselves.

As well as emotions, under "feelings" we can include other non-logical things such as hunches, dreams, visions and revelations. Reason does not preclude these. What it precludes is taking them at face value – even more so than taking perceptions at face value. The evidence of your senses comes from the world around you, from what is. A hunch or revelation comes from within, and how do you know what it's based on? Is it from subconscious pattern recognition – good or flawed – or from random subconscious activity throwing up wild ideas – good or flawed? In any case, they are not derived directly from reality, but from within you. To be confirmed – to become part of your knowledge – requires that they be tested against that reality: integrated without contradiction into your other knowledge. A feeling which flies in the face of the evidence of your senses has to be rejected as inconsistent with reality: as wrong.

Feelings are notoriously unreliable: you just need to observe the host of conflicting religions and the self-deceptions that come from taking feelings as facts. Look at the number of people who feel sure that their religion is right, but later fall away from it in disillusion: not to mention those who are equally sure of sundry other opposing religions. Look at the number of romantic relationships based on nothing but wishful thinking, which start with declarations of undying love (truly felt) but end within months. Feelings are to be enjoyed, but not accepted without thought. Hunches and other activities of your subconscious are a valuable part of creative problem-solving: but not a magic ticket to truth. The only way to understand reality is to look at it and identify it for what it is.

People Often Lie

People, of course, do lie and make mistakes. This is partly why unsupported human testimony is one of the least reliable sources of knowledge.

It is even worse when the testimony isn't first hand: then you have to deal not only with the possibility of observational errors, mistaken interpretations or plain lying by the primary sources, but with the distortions that occur during serial transmission. The party game "Chinese Whispers", in which a simple story is passed from person to person, is an instructive example of this distortion, which increases when the story is interesting. It is easily shown that people notice most what interests them or fits their biases, and like to improve it on the retelling!

However, that you shouldn't believe everything you hear doesn't mean you shouldn't believe anything you hear. Indeed, to believe nothing would be to cut yourself off from one of the main benefits of living with other people: the advantages of specialisation, which includes and requires specialisation of knowledge. So how do you judge the reliability of the people on whose knowledge you rely?

The basic rule of thinking is that all knowledge must be based on reason applied to perception of reality. A corollary is the virtue of independence: let no man's claims come between you and your own perception of reality. The two primary tests of the reliability of another person reflect these: What is the basis of their claims?, and Are their claims consistent with what you already know?

If their knowledge can in fact be classified as knowledge, because they base it ultimately on observation and reason, then you can have far more confidence in their pronouncements than if they go misty-eyed and speak of their or some guru's feelings and mystical revelations – in which you should have no confidence at all. There is only one reason for a person refusing to prove his claims: knowing he can't. The validity of a person's method of knowledge is the sine qua non of giving them any credence at all. Most people realise this when they deal with mechanics and electricians. It is a pity so many are less careful when dealing with values, and the meaning and goals of their life.

If a claim passes that test, does it contradict something you already know? If so, one of you is wrong. If the truth is important in this case, you need to examine the evidence and logic – yours and theirs. Reality and reason are the final arbiters of all disagreements. That someone's claims conflict with your knowledge indicates someone is wrong: but it isn't necessarily them!

A secondary test of another person's reliability is their character and intelligence. Are their claims of fact true, and is their reasoning from those facts sound? So you need to judge their honesty, accuracy as observers, and (if you need to rely on their thinking as well) their reasoning ability.

What about the opinions of "mankind in general"? What is the cognitive value of the beliefs of the majority? Opinion polls are useful if you need to know what people think, but are of little use in determining the truth. By definition, when any new truth is discovered the vast majority haven't even heard of it. In a society where people are taught how to think, the results of opinion polls would have a better chance of coinciding with the truth than in a society where irrationality is encouraged. But truth is determined by reference to reality, not by reference to other people's opinions. As Einstein once commented on a book entitled "101 Scientists Against Einstein": "If I was wrong, one would have been enough!"

How Extraordinary!

A specific part of the rules of human testimony concerns extraordinary claims. The principle here is well known: extraordinary claims require extraordinary evidence.

An extraordinary claim is one which flies in the face of existing knowledge, for example, a claim to be in communication with aliens or to have invented an antigravity device. The reason that extraordinary evidence is required derives from the basic principle that your knowledge must be integrated into a non-contradictory whole. If you are rational and your existing knowledge is not held lightly or loosely, but has been derived by proper principles of reasoning and evidence, then a claim which contradicts it – or is highly unlikely in its context – is up against all the prior evidence upon which your beliefs were based.

Thus, if your neighbour tells you "a car drove past 5 minutes ago", then usually you can take his word for it. If cars drive by often and your neighbour is honest, there's no reason not to believe it. But if he says "a flying saucer flew past 5 minutes ago", he'd need more proof!

On the other hand, as the first rule of induction is that facts cannot be ignored, if extraordinary proof is supplied, then you must modify your beliefs accordingly! Like everything else, the principle is not dogmatism but reason. Perhaps the best statement of how to deal with extraordinary claims is Hume's maxim:

That no testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact which it endeavours to establish.

Did You Hear the One About...?

This brings us to anecdotal evidence.

Anecdotal evidence is simply the things people report having happened. It has little cognitive value as a means for proving general truths (though it can have value as evidence for specific occurrences).

Its lack of value is not primarily a matter of doubting what people say, though that is part of it. Much anecdotal evidence is true. The issue is mainly one of coincidence. Trillions of events happen in the world every day, and while rare coincidences might be rare in any individual's life, they are not rare at all when summed over the experience of all mankind. "A followed B, and that is so unlikely to happen by chance that there must be a link", is invalid reasoning. The probability that it happened by chance has to be calculated, not assumed. And that is precisely what anecdotal evidence cannot do.

For example, an old medical scam is to sell a "cure" for an "incurable" disease such as cancer or arthritis, quoting "success stories" as proof of its efficacy. Even if those stories are all true, they prove nothing: inevitably, there are cases where remission or improvement happen by the natural course of events. Only a proper scientific study can demonstrate an actual causal link.

To rely on anecdotal evidence is to commit the logical fallacy of post hoc ergo propter hoc: that is, concluding from B follows A that A causes B. For example, a person might have seen with their own eyes that a person with Ebola got better after eating a snail. But 5% of people with Ebola get better anyway. The question is not "does B sometimes follow A?", as B can often follow A purely by chance. The question is "does B follow A more often than would happen by chance?" And if the answer is yes, the further question is does A cause B, or is there some other explanation?

This does not mean that anecdotal evidence has no value. It can be the first clue to a causal link or even to the existence of a new phenomenon. But it cannot itself prove anything: the hypothesis of a link has to be tested by proper experimental, observational and/or statistical methods. An hypothesis based on anecdotal evidence can be worth testing. But an actual claim to a causal link based only on anecdotal evidence is invalid and worthless.