Humans Cannot Have Certain Knowledge
And considerations about the significance of this limit
“I have approximate answers and possible beliefs and different degrees of uncertainty about different things, but I am not absolutely sure of anything and there are many things I don't know anything about”-- Physics Nobel Prize winner Richard Feynman
Any theory of knowledge, including in mathematics, science, and logic, cannot be certain, and no human beliefs, theories or models can ultimately be proven certain.
All statements of knowledge can be questioned as to their veracity, and, for certainty, must be proved true. There are three ways to try to answer questioned statements: 1) circular argument, 2) infinite regression, or 3) axiomatic argument. Each is incapable of finding certainty.
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Circular reasoning, or begging the question
This is when you use the statement to (try to) prove it true:
John: “God is real.”
Mary: “What is your justification for believing that true?”
John: “The Bible says God is real.”
Mary: “What is your justification for believing the Bible is true?”
John: “The Bible is the word of God.”
The above is circular reasoning because John said God is real because God is real.
Nancy: “My sight is reliable.”
Pat: “Why do you say that?”
Nancy: “Because my eyes see that apple.”
Pat: “How do you know the apple is real and really there?”
Nancy: “Because I can see it sitting right there.”
Nancy is arguing that her sight is reliable because her sight is reliable.
A logician saying human logic is correct because human logic has shown so is using circular reasoning. Science saying science proves that science is reliable is circular reasoning. No belief system, theory or way of thinking can prove itself true or accurate, or even know its own reliability.
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2) Infinite regression
This is like the young child who continually asks “But why?” to every answer you give.
A is true because of B
B is true because of C
C is true because of D
Repeat until infinity
Carl: “My sight perception is an accurate perception of reality”
Charlie: “How do you know that?”
Carl: “Because I took an eye test last week.”
Charlie: “How do you know the eye test is reliable?”
Carl: “Because it was performed by an optometrist who is an expert in eyes,”
Charlie: “How does the optometrist know that eyesight is an accurate representation of physical reality?”
Repeat until infinity or one quits in frustration or boredom.
Some like this line of reasoning because it can involve lengthy analysis without being proven wrong. However, it will never reach certainty because the questions continue forever.
Infinite regression is an elongated way of saying “I don’t know” or “I’m not entirely certain. I have to look into it further.” However, good long arguments can be considered provisional truths. This means they are working answers that are considered true for the time being, though one knows they may be found to be false in the future. It is likely that longer down the line you get, you will find questions you can’t answer or answers that contradict the belief.
Philosopher Henryk Skolimowski wrote, “The more deeply we explore any subject matter the more surely we are going to arrive at unexplained phenomena which challenge the entire framework of our quest for knowledge . . . The pursuit of knowledge is the pursuit from comprehension to incomprehension. We always start with something we know fairly well and end up with big puzzles.”
Humans must be prepared for their rules to be proven wrong, or at least having exceptions and needing refinements.
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3) Axiomatic argument
This involves making unproven and often unprovable assumptions, called axioms.
John: “My sight perception gives a reliable view of physical nature.”
Nancy: “How do you come to that conclusion?”
John: “I assume my perception is reliable. Don’t you assume yours is?”
All human endeavors, including yours and mine and those of the most famous thinkers, involve unproven or unprovable assumptions. Circular reasoning can be considered a form of axiomatic reasoning. “I believe God is real, because (I assume) God is real.”
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Considerations about the significance of this limit
While it is simply fact that humans cannot have certain knowledge, there is a wide variety of considerations of the significance of this uncertainty.
To some, the lack of certainty is profound. If one is concerned with the search for metaphysical and objective truths about reality, the inability to know even the reliability of one's own sensory perception can give angst.
To others, the uncertainty does not bother them. Some may rightly say that, yes, there is uncertainty in all things including science, but science still produces reliable results. There is much unknown about quantum physics but it makes accurate predictions. There are uncertainties in engineering, but it is used to build sturdy bridges and working cars. To many engineers, the inability to know the meaning of the universe and the fact that many areas lay outside of science are beside the point to their work.
Many people can psychologically live in uncertainty better than others. Some psychologically need answers, while others do not. Many people live their entire lives unaware of this uncertainty.
Further, many of the greatest and proudest achievements of humans are the products of uncertainty. Many great artworks, many scientific and knowledge discoveries, are the products of being faced with mystery. This essay is the product of knowing one cannot know, and having a desire to study this lack of knowledge.
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Further reading:
The Nature and Limits of Science
Your opening quotation, and the article in general, made me think of René Descarte’s attempt to get at certain knowledge by first doubting everything and stripping away everything formerly known. He decided that the very act of doubting meant that there was thinking, and thinking meant that there must be a thinker. “I think, therefore I am.” When I took a philosophy class years ago, a professor led the class to the conclusion that Descartes had failed to doubt the assumption that an action must always have a thing doing the action. According to this view, the most that can be said is “thinking is going on.”
A wonderful essay on infinite regression is Lewis Carroll's "What the Tortoise Said to Achilles," which I read in the anthology *The World of Mathematics," edited by James R. Newman, circa 1960.