A post at the New Order Mormon discussion board got me to thinking about the question of what we can really "know" in life. One commenter mentioned that some philosophers have postulated that a person can never really know anything. I think this may be correct if one equates knowledge with certainty. That is, I think it may be true that one can never really know anything with absolute certainty. However, I find equating knowledge with certainty an unsatisfactory way of looking at the issue.
I like to think of knowing something as simply perceiving or understanding information. Things can be known with varying degrees of certainty. Knowledge and certainty are not the same thing, though they are often used interchangeably.
For example, when I say that I know that the moon is not made of green cheese, I will grant the philosophers the point that I don't really know that with absolute certainty. However, I do know it with a very high degree of probability that approaches certitude, say 99.9999% certainty. My knowledge of this fact is based upon my perception of information I have received and my evaluation of that information in light of my life experience. The list of things in life that I can say I know to a similar degree of probability approaching certainty is long. Columbia is the capital of South Carolina. The Alamo is located in San Antonio, Texas. Light travels at approximately 186,000 miles per second. I hate coconut. Tom Cruise is a nutjob. Etc.
There also are things I can say I know with a reasonable degree of certainty, but not really approaching absolute certainty, say 75% certainty. For example, the Texas Rangers will not win the World Series this year. Jack Bauer will not die on 24. Lee Harvey Oswald killed John F. Kennedy.
Of course, some folks will claim to know things to a degree of probability approaching absolute certainty that I know to be false to an equally high degree of certainty. For example, let's say I have a friend named George who claims to know to a high degree of certainty that extraterrestrials in spaceships have visited the earth, abducted numerous people, and performed all sorts of experiments upon them. While I cannot say with absolute surety that such things have not, in fact, occurred, I think it is fair to say that my perception of information I have received and evaluated in light of my life experience confers on me knowledge to a high degree of probability approaching certitude that aliens have not been visiting the earth, abducting humans, and performing experiments on them.
This leaves us in something of a quandary: with respect to this single proposition on the alien visitation issue I know one thing with a high degree of certainty and George knows with a high degree of certainty something diametrically opposed to my knowledge.
This is where rationalism comes into play. For while it is fair to say that, all other things being equal, my personal knowledge on the alien visitation question and George's personal knowledge on the same issue are entitled to equal respect, all other things are not equal. We have to consider not only our own personal subjective perception of information but also the combined perceptions and experiences of the rest of humanity--their judgment must inform our own judgment. In the example given, George's knowledge is probably based on his own experience combined with an unreasonable reliance on sources lacking credibility. My knowledge is based on my own experience along with a reasonable reliance on the judgment and experience of people who have studied the matter scientifically, i.e., who are credible.
I submit that not all knowledge is equal. Some knowledge is subjective only. Some knowledge is based on unreasonable reliance on sources lacking credibility. Some knowledge is based upon a combination of personal experience and reasonable reliance upon credible sources.
So the next time I hear someone say they know something with absolute certitude (maybe they will even say they know it with "every fiber of their being"), I will not contend that they do not know what they claim to know. I will simply ask myself: is their knowledge based on their own personal experience along with a reasonable reliance on credible sources or is it based on their own personal experience combined with an unreasonable reliance on sources of questionable credibility? If the former, I may be able to learn something useful; if the latter, I will give little credence to their statements.