Optical illusions provide an analogy for the way that beliefs shape our world. Take for example the classic glass/face illusion. As we look at the image we either see two faces looking at each other or a goblet with a fluted stem. If you sit still and look at the image, the sensory information you receive through your eyes will remain the same, but you may see either the goblet or the faces. Generally you cannot see both at the same time. Once an interpretation has been made, other interpretations are suppressed for a while. This is particularly the case for the illusion lower on the page which can be either a young woman or an old maid.
The power of interpretation is not limited to seeing, it is universal and applies just as much to our interpretation of news stories as it does to the motivations we attribute to other peoples actions.
The power of belief to effect our perception is at its most visible when we argue. Two sides can argue forever, both amazed at the stupidity of their opposition who are apparently unable to perceive that which is obvious. The long held beliefs of each side act as filters preventing them from perceiving things which would contradict their beliefs. Their opponents arguments effectively come from another world.
These are some of the more obvious effects of belief, but perhaps the least important ones. More important are the subtle ways in which our beliefs shape our worlds. Depending on what we believe the world in which we exist can seem to be welcoming or cold, benign or malign, because the world in which we live, is an interpretation of reality, not reality itself.
So assuming the reader now accepts that belief is important, the question is what to believe. I have no intention of trying to tell anyone what they should believe. For the reasons stated above this is rarely a productive strategy. Instead I will propose a method which can be used to rationally decide what to believe, even in the face of a complete lack of good evidence either way.
The two grounds for belief
At the simplest level there are only two reasons we might believe in something. The first is that there is good evidence for its truth or existence. The second is that the belief is held for its own sake, because of the effect that holding the belief will have on ourselves and on others.
Most people should be familiar with the idea of evidence, either in the context of a trial, or in the context of a scientific experiment. There are clearly many occasions when evidence is and should be the main criterion we use to judge whether a belief is sensible or more importantly whether it is good. When deciding whether water is safe to drink is better to subject is to a thorough chemical and microbiological analysis than it is to take its cleanliness as a matter of faith. This and a great many other things are relatively easy to test, and can be proven to a fair degree of certainty within a reasonable amount of time. But we don't have to look too far to find examples where evidence and experiments are of limited usefulness. Imagine you are in a bar, and an attractive man or women (reader's choice) looks towards you and smiles. Imagine also that you are interested in them. If the bar is even somewhat crowded, you can never really be sure whether he/she was smiling at you or at the person next to you. Worse, maybe he/she wasn't actually smiling, but was in fact struggling to suppress manic laughter at your ridiculous choice of clothes. It would certainly possible to devise some experiments which might help you decide on way or another, but the chances are that the opportunity will have passed long before any real certainty is achieved.
In this situation you can never be sure where the truth lies, until you risk rejection and go and talk to them, or at least smile back. If you are confident, or just a born optimist, you will probably see them as smiling at you, and interpret this as an invitation to start a conversation. If you are desperately insecure, you might think that they were laughing at you, you probably won't go and talk to them, and even if you do you may come across as being uncomfortable, defensive or hostile.
Even in this everyday situation, a situation which we wouldn't normally think of as lying in the realms of belief or faith, the outcome is very strongly dependent on what you believe. Because of this it starts to be the case that the balance of evidence is no longer the only thing to consider when deciding what to believe. In this situation, it also makes sense to consider the effect that the belief itself will have on you and on those around you. Clearly the positive belief is better for you, it is better to be surprised by a few unflattering responses to your attempts at conversation, than it is to go around believing that everyone is ridiculing you. Not to mention the non-zero chance that you might get to go home with the man/woman of your choice.
Now having seen the intermediate, we can look at the complete opposite end of the spectrum. There are some sets of beliefs, including those corresponding to religion, which are constructed in such a way that they are impossible to prove or disprove. They make no predictions which can be tested. One approach toward such beliefs would be to state that they are all equally valid since no evidence can ever be given which would suggest that one belief is better than the other. As some hardcore atheists have pointed out if we restrict ourselves to the use of evidence, then we might just as well believe in an "invisible pink unicorn (IPU)" as in the existence of a god or gods. The amount of evidence for the IPU is exactly the same amount as that which we have for the existence of a god who refuses to prove his existence because he requires faith on the part of his followers.
This is clearly a rather silly result, and to deal with it we need another basis on which we can evaluate beliefs. That is, we can evaluate the beliefs based on their effects. If the effect of a belief on those who hold it and on those around them is good, the belief itself is good, if the effects of the belief are bad, the belief itself is bad. Bear in mind, this is not intended to give anyone carte blanche for huge flights of wishful thinking, it is merely the only rule which can be sensibly applied in situations where evidence is impossible.
Clearly this rule can lead to loops of logic. For example imagine that group A decides to believe that everyone that they kill in battle in the next fifteen days will be taken up to paradise. From their point of view, the very best thing they can do is to massacre as many people as possible within the fifteen day paradise window. The problem being that the people being killed don't share group A's beliefs and object most strenuously to being slaughtered in their thousands. The only solution to this problem is to evaluate the effects of a belief, from the perspective of those who do not subscribe to it. Thus before embarking on their beneficent murder tour, group A must consider if it the best thing for the potential victims/beneficiaries, based on their own beliefs, not those of group A. Essentially, since there is no evidence, group A must consider that they might well be wrong.
This may seem a little over strict, but most of the worst excesses which have been attributed to one religious group or another in history, arise from the kind of circular thinking which group A was tempted to indulge in above.
Optimism and Pessimism: Meta Beliefs
Optimism and pessimism are meta-beliefs. If we return to the bar in our example earlier the optimist will interpret what he sees differently to the pessimist because he believes that the positive interpretations are more likely to be true than the negative ones. Hence the name "meta beliefs" i.e. beliefs about beliefs. We can even take this one level deeper, and get to something fundamental about the personality of the optimist and the pessimist. Both the optimist and the pessimist tend to view each other as fools. The optimist sees the pessimist as a man who, without good reason, makes his world into a dark and unfriendly place. As someone who is always getting everybody down. Conversely the pessimist sees the optimist as a fantasist, who lives in a world of his own which bears little relation to reality and expects that at any moment the optimists world will fall apart around him as the ugly merciless truth puts a knife through the neck of his dreams.
Naturally as with all other disagreements, both sides claim the moral high ground. The pessimist states that the optimist never has the truth, that the optimist has an ulterior motive but he does not. This is however a conceit, the ulterior motive of the pessimist, is the feeling of superiority he gets from freely choosing a painful and difficult path. The optimist sees himself as the bearer of hope, the one who dares to believe and to try knowing he may fail but continuing regardless. The danger is of course that his hopes may truly be unfounded, and that he wastes his own efforts and those of others in pursuit of a mirage.
Neither optimism nor pessimism is consistently the right choice. Both are biases, but when the truth is uncertain, and evidence scant, being biased one way or the other is unavoidable. Thus the real question is when to be an optimist and when to be a pessimist. Once again, this comes down to considering the consequences of our beliefs. An engineer building a bridge or an aeroplane must be professionally pessimistic, if he is to produce a structure which will withstand as far as possible the worst that nature and chance can throw at it. Conversely to be pessimistic about human nature, is hugely destructive. For a true misanthrope kindness appears to stem either from weakness or hidden self-interest and fidelity is the preserve of the ugly. In short the misanthrope lives in a hell entirely of his own construction, with self-importance as his only consolation.
Can we really choose what we believe?
This whole piece has been an attempt to provide the reader with the tools to decide what they should believe. So if we cannot choose what we believe then it has been a waste of time. It is a common belief, that our beliefs are fixed, that we are not free to choose what we believe. We have already discussed how beliefs persist and arguments continue because our beliefs act as filters for our perception. So how can we ever change our minds, and rationally decide what to believe?
The solution to this is simpler than you might imagine. Simply being aware of the effects that our beliefs have on our perception, frees us to some extent from their power and enables us to view the world from other perspectives. Once we have decided what to believe, we can then fix that belief by examining the world in the light of the new belief and looking at the form which it takes on. If we so decide then we can further fix the belief by acting at all times as if it were true. The mind does not deal well with contradictions between thought and action, and after sufficient time the actions will cement the belief. In this way, we can decide rationally on what to believe and thus shape for ourselves the world in which we live.
So be careful who you pretend to be and be careful what you believe.