How We Know What We Know
Realizing how we know what we know makes us aware of the limits of our knowledge. If we think we understand the world better than we really do, we are bound to experience many disappointments and unpleasant surprises.
The solipsist believes that everything in the world is an illusion — that what we think we see has no necessary relation to reality. It’s a logically unassailable position but an impossible one to maintain for any length of time. The impact of our sensory inputs is too great just to be pushed aside.
The most obvious way we know something is by observation through our five senses. Observations may be direct (I see it’s raining and I hear thunder) or indirect (my battery tester tells me that this battery is dead). But what we observe is not always what is actually happening. Professional magicians, for instance, are experts in creating illusions. Eyewitness testimony in court is often later proven to be mistaken. Measuring instruments can malfunction and give incorrect readings.
Another way we know things is through memory — the storage of knowledge. Memory tells us about the past, but our memories are sometimes mistaken.
We can know things — or think we know them — through intuition. Intuition accounts for our knowing things without knowing how we know them. Intuition by its nature cannot be shared; what I know intuitively can only be justified to other people by resorting to some other form of knowledge.
Closely related to intuition is divine inspiration. For those who experience it, this sort of knowledge is intense and beyond question. But divine inspiration, like intuition, is not directly communicable. It can, however, be contagious, as it often is in prayer meetings.
We can know things is through reasoning and logic, but reasoning and logic are vulnerable to errors. We often cite “2+2=4” as an example of something that’s obviously true, but how about 3975 x 6231=24,768,225? It’s true but it’s not obviously true; you need to verify it with a calculator or with a long and error-prone hand calculation. Interestingly, there are mathematical statements that are undecidable — that is, they can neither be proven true nor false. (That is the essence of the Godel Incompleteness Theorem.)
Perhaps the most interesting source of knowledge is testimony — what other people tell us. We are deluged by testimony — reports, stories, advertisements, gossip, news, advice, educational materials, and much else. Even our scientific knowledge is based on the testimony of scientists, most of which the average person has no way of verifying directly.
How can we know what testimony to believe? Often we can’t, particularly when it comes to people who are trying to sell us something. Advertisements are a pervasive source of testimony, carefully designed to be as convincing and believable as possible. A few of them are truthful; far more are exaggerations or deceptions.
Gauging the reliability of testimony can be very difficult. Someone can make a convincing case for a hypothesis and still be wrong. When the subject is something you don’t already know much about, it’s not easy to spot the flaws in the argument. But several things can help in knowing what to believe: considering the source, looking for internal inconsistencies, and hearing the other side of the argument.
An instructive example is the ongoing dispute over evolution and the biblical account of creation. Within the scientific community there is almost total consensus that evolution accounts for how humans came to be and that the biblical account of creation is a myth. Yet there are people with impressive academic credentials who defend the biblical account, people who clearly are neither unintelligent nor uninformed. Their extensive knowledge can make it very difficult for those who haven’t studied the matter to see what is wrong with their arguments.
What the creationists obviously are, however, is hopelessly biased; they start with unquestioned assumptions based on their religious faith, usually fundamentalist Christianity, and shoehorn the facts into those assumptions. Knowing that bias should make you immediately suspicious of their case. Another consideration is the implausible chronology of the creation according to Genesis, which places the creation of the earth before the creation of the sun. Believing that would require denying just about all of astronomy.
As another example, consider the Kennedy assassination. No one seems to doubt that Kennedy was indeed assassinated at Dealey Plaza in Dallas on November 23, 1963, but many people question the conclusion of the Warren Commission that Kennedy was killed by a single bullet fired by Lee Harvey Oswald. Quite a few of them marshall an impressive array of evidence involving ballistics, photographs, and documents to support their explanations.
But there are many conspiracy theories and they can’t all be right. A non-expert has no way of evaluating any of the arguments with confidence; you ultimately have to rely on your own judgment of whom to believe, taking into consideration what you know of the reliability of the testifiers, their biases, and the apparent consistency and completeness of their claims. For me the composition of the Warren Commission is a strong argument for the correctness of its main conclusions, even if the commission may have gotten some of the details wrong.
So confidence in what we know should be contingent and relative. Yet we have to assume that what we know with certainty is indeed true; life without that assumption would be unmanageable.
Ultimately, the only sure knowledge we have is that of our emotions and feelings. What I perceive in the world may be an illusion, but the fact that I’m perceiving it is not an illusion and cannot be denied. If I’m feeling excited, or happy, or sad, or in pain, there’s no denying that that is what I’m feeling. If I lose a limb, my sense of a phantom limb is undeniable even if the limb itself is not there. No other knowledge can be as certain and correct as that.
