What is a belief? according to the dictionary belief is: a principle or idea, etc. accepted as true, especially without proof (Harrap's Chamber 2005). As for the verb to believe: to accept (something) as true.
The belief is bound to a frame of mind that generates a certain reality. This state of mind was (and still is) built by education (from parents, teachers, surrounding people, and so on), and bad or good personal experiences we underwent during our life. Those two process are the major contributors to our beliefs.
We tend to associate belief with spirituality and therefor the religions whichever they are (monotheism, polytheism, or animism, etc.). The main reason being that because spirituality cannot be quantified, it cannot be proved.
Spirituality is essentially the belief in the afterlife. Generally you find a paradise and a hell managed one or many gods and demons with the possibility to be reincarnated there or not (according to some religions). And if it is only the imagination's results of our naive ancestors, then it's quite elaborated, as there are many structured heavens and hells. The one or many gods ruling them are followed by a complex hierarchy. But spirituality also talk about magic and it's succession of magicians and sorcerers, jinns, fairies, parallel worlds, the different types that it's (magic) made of, chakras, etc. Legends and tales are stories about spirituality.
There are also methods of learning sorcery which are kept secret for most of them. However few have been revealed: Carlos Castaneda, for example, has told about some methods in his books. Yoga (practiced in India under the strict supervision of a guru) is another one.
Finally, esotericism is a hidden face of spirituality given to few selected initiated people.
But, spirituality not being material, it is impossible to prove what it says. We don't doubt god (or the gods). He exists, that's it. We must have faith in him, not to think about him, but to feel him into our heart. Then he reveal himself into us. Others can keep their doubts. God doesn't have to justify himself to men. We're the ones who have to go to him. God is only our own divinity and if we reject him we will lose faith in ourself. Here is some logic of spirituality. The danger of that logic is to confuse god's will with our own desires and interests.
Those who claims that they believe in nothing are not being very honest. Because, in the absolute, it's difficult to believe in nothing: there is always something we connect to. The majority of 'non-believers' believes in evolution or in science (one going hand to hand (but not always) with the other).
There are, of course, the clues that we all know: skeletons, tools, ruins of villages (or camps) that have been found across the world that fuel the evolution theory. Having said that, there are still many missing links to give it its continuity and therefor providing the proof that it is the true history of the world.
On top of that, there are many anomalies such as the ruins of cities that contradict the theory (remnants of cities have been found coming from a time where there was supposedly only villages ruled by brutes), strange objects, or skeletons of giants and other strange creatures which are many small rocks blocking that beautiful machinery of evolution.
To counter them, they are being ridiculed as hoax (by panels of 'experts'), and if they cannot be, they are simply ignored.
"I only believe what my own eyes show me" is often the rhetoric asserted by the 'non-believers'. what would they say, if they saw a ghost, for example? Well, they would not even believe their own eyes (contradicting their first assertion), claiming to be victim of an hallucination. Hallucination being a good excuse they hide behind, when they cannot explain something they don't understand. Paradoxically, they make fun of those who say "it's god's will" when they cannot explain what they don't understand.
Finally, the two main theories of materialism (the cradle of evolutionism), the Quantum and the General Relativity theories seems to be in conflict (link for those who can read French) with each other to see which one is correct. Also, another article (I cannot find but, you can on the site of the link above, if you look for it (remember it's in French)) claim that neither of the two theories actually can define what truly mater is, even after they tried to connect them together.
The good side of science is this perpetual readiness for changes and this open mindedness of those who chose this path. Because, it is not the researchers, generally speaking, that claim that their discoveries are the truth, but the mass media that relays them and are so ready to repeat what they hear without seldom questioning what they're repeating.
Okay, I am deviating from my subject. I want to come back to what I was mentioning at the beginning of this article: the state of mind. Science, more than just a process, is a frame of mind resulting from rationalism, itself emerging from materialism. Its key word is the doubt that we use until we find the proof that will put an end to it. It is the antithesis of faith: trust or confidence, strong belief (according the dictionary).
However, science needs some sort of conviction (such as strong belief) to prevail, because, by maintaining doubt permanently, it might enter a dead-end.
Therefor, science sails between doubt and a strong belief of the superiority of the elements over men, creating dogmas and burning on a bonfire of ridicules all deviants.
When the conviction has deeply anchored itself in the person adopting that state of mind, then, through his perception of the world, everything he will see and that will happen to him will feed his conviction, because the explanation he will find by his reasoning, forged by his belief, will convince him of its veracity. The experiences that he will make to prove a theory, will be conducted in such a manner (distant from nature's ways) that will maximize its chances of success. From what he will observe, he will be able to say: "I saw it from my own eyes, therefor it can only be objective". Except, it will be the conclusion, he will reach, influenced by his own convictions, that will be subjective. Because, before being scientists, they are human beings. And man is known to make mistakes, influenced by a distorted judgment (from beliefs).
Every body knows, when an event occurs (an accident for example), each witness will give his own version of what he saw. So the testimonies will differ from one witness to the other.
what distorts our objectivity are our personal moral values, which we cannot dissociate from our observations.
I tend to criticize a lot the scientist, knowing that the spiritual is as much subjected to those influences. But if everyone knows that spirituality is a matter of belief, no one seems to be aware that it"s the same with materialism (as well as rationalism which emanates from it and from which the scientific mind result). I just wanted to point that out.