Just about every person has doubts. Doubt is a feeling that gives us pause to consider our beliefs. Doubt is very important. The problem with beliefs is that traditionally everyone was cocooned in to a small community called a tribe. If you doubted tribal norms and customs, you would have very little outlet. At the risk of being ostracized, or worse, the best course of action was to quell your doubts. You had to convince yourself of the rectitude of your tribe. To think otherwise would just relegate you to misery, and to express it was unthinkable.
Eventually societies grew into city states. Social circles grew larger, and consequently any deviation from the norm of the tribe would be okay within the city state. Cities were the first places where people with multiple beliefs could actually get along. There were places in Roman cities for instance were very multicultural, and you could live much freer there than under the communitarian rule of a tribe, where everyone's business was everyone elses business too.
But there was still a limit. People were still under the impression that locality meant the only true way of life. Travel and trade changed this. People started to look elsewhere and see other places where people thought they were also right in their customs and beliefs, and this engaged another wave of doubt in humanity. Trade hubs in the ancient world were always very liberal and progressive as opposed to their more insular cousins elsewhere in the realms. People had to get along to engage in gentle commerce, so a heathen meant a profit. It also meant that we could do what all humans do, namely form relationships with our fellow man. In this case we could cross pollinate our knowledge with theirs. This was a massive move in pushing society forward. In fact the black death was responsible in part for the regressive dark ages because societies became more insular due to dwindling numbers.
The next wave of human doubt came at the beginning of printing and general literacy. Being able to read meant no longer only getting the opinions and views of those you are in direct contact with, it also meant reading the views and opinions of those you may never have come into contact with. A good idea could spread and instill doubt in those who thought that their immediate contacts were right and true in their beliefs. Literacy and printing were in large part the reason for the protestant reformation, the reclamation of religion out of the ruling papacy, and the enlightenment, philosophy and science that nudged the world closer to the modern day. People could read Plato and Aristotle and Epicurus, and had to incorporate this knowledge into their world views. The enlightenment largely affected the intellectual classes of the time, and this had massive sweeping effects on technology, but the philosophy did not reach the common man. It took some elite education mostly to get a hold of these ideas, and most enlightenment guys were part of some sort of aristocracy. But things are changing.
In the previous paragraphs I have explored the limitations to the reach of contrary worldviews, namely first that a small tribe disallowed dissenting views, secondly that cities allowed a larger circle but were limited by local upbringing of residents, thirdly that contrary views were limited to those who had personal contact with everyone, and finally that an aristocratic education was necessary to understand and spark interest in philosophy and science.
The final limitation is falling away with the advent of the internet. Fairly soon the best education will be available to every single human being, if they choose to make use of it. The intellectual growth of mankind is already evident, I myself being an example. I am not a native english speaker, but I can look up words online, along with their etymologies, connotations, antonyms or common usage for example. Other topics are open to all, and this instills the final wave of doubt. Given all this information, how can we incorporate it into our worldviews? The only limit that stands in our way now is our own bias and our own laziness. I am generally positive. I think we can embrace the final wave of doubt and enter into a new era of enlightenment, where all of humanity has matured. I know it might seem difficult to see from our current vantage point, but a look back into history provides a much more positive view, and I hope this post drives that idea home.