Our brain is a vast collection of neuron cells with complex connections between them, a neural network. When we learn, it might create new connections between the neurons or increase/decrease the strength of the existing connections. This is how our brain creates models based on different sensory inputs (eyes, ears, etc.). Here, a model's strength or belief depends on its probability (how often occurred, told, etc). As we learn, the model's belief probability (and hence connection strength) might increase or decrease. We lead our life by understanding...judging our life and the world using these models. None of the information that goes from our senses to the brain is totally complete or accurate. Intelligence is about inferring and predicting from the incomplete information! As everything is incomplete, everything is a belief; though, each belief may have different probability. Everyone's blind-belief is also just a belief from their brain point of view. Hence, our belief is subjective. So, we need an un-biased objective look and research (science). This is what many great minds including Galileo showed us. But, how to make everybody to believe/understand this?
There are few important factors for anything to evolve: (1) storage place, (2) making copy, (3) errors during copy making. For example the 'genes' are stored in DNA, their copy making is known as reproduction and the errors are known as mutations. Evolution does not know or care about good or bad; just the fittest for the situation/environment survive and grow. Another example for the evolution is the 'memes'. A meme refers an idea, such as god, religion, science, astrology, ghost, socialism, capitalism, communism, democracy, etc. The memes are stored in the brain; they are copied to other brains through language and society; and of course everybody gets them differently (subjective errors). Just like the genes, there are millions and millions died-out memes. There are millions and millions died-out gods. All the existing memes are survived and evolved over the time depending on the situations. In those situations, our basic emotions (emotions are from the genes evolution) play a major role in shaping many blind-beliefs. During initial stages of human history fear and ignorance might have played a role for many blind-beliefs. Now, they might exist as totally modified and highly evolved memes. As language and society are critical factors for the memes to evolve, we see blind-beliefs and science in humans, not in other animals.
Critical thinking is to analyze everything objectively and learn appropriately to form belief probabilities. But, it is also a skill to be learned from our childhood that ultimately depends on the environment we live and grow-up. When we lack proper critical thinking, our brain learns without much objective checking and form belief probabilities. This might lead to blind-beliefs that are opposite to objective knowledge. The brain models created without proper critical thinking might be inconsistent, chaotic and inefficient. In any case, critical thinking does not mean to accept only the thinking-part of brain, but the emotion-part as well. It is critical thinking to accept certain customs to satisfy human emotions and social integrity. It is critical thinking to mourn and erect memorable symbols for the dead, and sing and celebrate birthdays and new years. Critical thinking is not about what we do, but how we do, whether with good understanding or just blindly.
(On November 19, 2009)
Based on the comments that I have received, I would like to add some further analysis about subjectivity, objectivity and critical thinking.
Subjectivity and Objectivity
Everything we think, feel and perceive is purely our own, i.e., subjective experience. For example, sometimes we feel that Time goes faster and other times slower. Not only we feel differently when compare to others, our own perception changes with respect to our mood and age. So, we look for external objective references or standards, like sun/moon cycles or pendulum/quartz/atomic clocks. Note that some standards are more accurate, consistent and reliable than others. In any case, objectivity is nothing but using a common external references or standards.
We have found and established good objective standards for many things, such as time, temperature, length and weight. We have also found and established a reasonably good objective standard known as science for how to learn and understand. Science is not a simple standard like time or temperature measurement, but a complex process. Science involves collecting data and evidences, creating theories and models, predicting new features, validating them, etc. Fundamentally, it requires being doubtful and demanding evidences, proofs and validities.
Critical thinking and Science
Everything we know about is fundamentally a belief, and it is just that its belief-probability (certainty) might be different. Some are more certain than others. The belief-probability for each one might be different for everybody and different for the same person at different time. It depends on how we develop belief-probability as we think and learn.
A simple straightforward thinking/learning might be OK for simple things, such as finding food and mates. But in a polluted memes environments, and as we expand our thoughts beyond finding food and mates to atoms and molecules, bacteria and viruses, solar system and galaxies, quantum worlds and cosmos, evolution and artificial intelligence, we need to develop a better thinking/learning skill. As we have seen before, the best objective standard known for this is a scientific approach – a critical thinking! That is to add an extra check in our thinking/learning skill to be doubtful, demanding evidences, proofs and validities, building consistent models in our mind, etc.
Objectivity for subjective issues
Finding objectivity (a common, accurate, consistent and reliable standard) for highly subjective issues can be very hard. For example, what is good or bad or fair? There is no fairness in nature itself. Things that were considered bad hundred years back are no longer bad today. What is good for me might be bad for others. What is good for one society or country might be bad for other. What is good for human might be bad for other species. Though, it is difficult to remove all the subjective elements, we have established and refined complex objective standard called law system (local, national and international laws).
For many different kinds of negotiation, the books mentioned below offer certain objective approach. Please refer: Negotiation Books Summary
Most of the social issues are highly subjective such as gay rights and healthcare for all. There is a possibility for some reasonable solutions for most of these issues based on objective knowledge and objective goals. But, if we fight for things like stem-cell research, then the hope for that possibility may not be near.