It is true that objective knowledge is not possible for human beings. All of our knowledge is subjective. Since we are subjects, it is obvious that whatever knowledge we have, we obtained as subjects and therefore is subjective. The information we receive is interpreted by us, not only in light of our worldview (set of presuppositions we have about how the world is and how it operates), which is what most objectors to the concept of objectivity have in mind, but also and equally important, in light of our life experiences, including our personal interactions and attachments with other people, our emotional frame of mind when we encounter the new information, psychological factors such as how the interpretation of the information impacts us personally, and our neurophysiological make-up. Neuroscientists are discovering that each one of us is wired somewhat differently. For example, some people are more prone to risk-taking and self-confidence and others are more prone to worry, contemplation, and low self-confidence. So, not only does worldview impact how one interprets the information that one receives but so does sociology, psychology, neurophysiology, as well as many other factors that one may not even be aware of. Each one of us is truly a unique individual.
To complicate matters even further, none of us has complete information. We are limited in our knowledge. We can only understand new information as it relates to information we already possess. So, unless one is omniscient, a perfect and complete interpretation of new data is impossible.
Thus, it might seem that true knowledge is impossible and we should all be like Descartes, doubting everything except that we doubt. I don't believe that kind of ultimate skepticism is demanded. I think we can achieve some degree of certainty about our knowledge through various checks and balances.
First, we must be aware as much as possible of all the factors mentioned above. We should realize that we are biased, that we are heavily influenced by our culture and by the people we know and respect, and that our emotions and our physiology can impact how we understand the data. While this awareness will not eliminate the subjectivity, it is a better safeguard than to be unaware of it. If a person knows that he is colorblind, he is more likely to rely on others to pick out what color tie matches his suit. We should consciously attempt to consider alternative viewpoints which don't share our same biases. We should periodically examine our biases (at least the ones we are aware of) and determine if they are justified. If we are politically liberal, we should watch Fox news on occasion and try to see things as the conservative does; on the other hand, if we are politically conservative, an occasional dose of MSNBC might be helpful. We must realize that people on the other side of our particular ideology are not necessarily dumb. They often have a strong intellectual case for their ideology which makes perfect logical sense within their set of assumptions.
Second, we must be aware of our limited information and refrain from attempting to formulate definitive conclusions until more "returns are in." We all remember the erroneous projections that television networks made in the 2000 election because of their premature assessment of the data. Human beings tend to be impatient. We want an answer and we want it now. This can often lead to a wrong interpretation of the information we have. We must be honest about what we don't know. A. N. Whitehead said: Not ignorance, but ignorance of ignorance, is the death of knowledge .
Third, we must be humble and willing to change our minds if another interpretation becomes more plausible. We all want to be right and hate to admit that we were ever wrong. We all have some degree of intellectual pride. We all have some emotional attachment to our beliefs. To forsake one way of thinking and adopt an alternative way for some people is as difficult as divorcing a spouse and remarrying. It is traumatic and we humans don't like trauma.
In view of all of the above, I choose to call myself an agnostic. Robert Burton, a neuroscientist writes:
Recognizing the limits of the mind to asses itself should be sufficient for us to dispense with the faded notion of certainty, yet it doesn't mean that we have to throw up our hands in a pique of postmodern nihilism. We thrive on idealized goals that can't be met. In criticizing the limits of reason and objectivity, I do not wish to suggest that properly conducted scientific studies don't give us a pretty good idea of when something is likely to be correct. To me, "pretty good" is a linguistic statistic that falls somewhere in between "more likely than not" and "beyond a reasonable doubt," yet avoids the pitfalls arising from the belief in complete objectivity (On Being Certain, pp. 175-176).So I agree with Clarence Darrow, the attorney who defended John Scopes in the famous "Scopes Monkey trial" of 1925: I do not consider it an insult, but rather a compliment to be called an agnostic. I do not pretend to know where many ignorant men are sure -- that is all that agnosticism means.