There are many ways to divide up knowledge, and they all have problems. This is the best I've come up with so far. The word "know" is used to express two concepts: ACQUAINTANCE and CERTITUDE.
e.g. to know Fred, your car, your face in the mirror
e.g. to know how to swim, or solve math problems
Distinction: to know X from not-X
Exhaustive familiarity: to know everything about X
First time encounter
Every day experience.
|Note the difference between probability and probability judgment. Probability itself is based on mathematics, and is therefore objective. But probability judgment is an opinion. It happens every time a mind makes a guess.|
CERTAINTY (not subject to error, 100% certitude)
1. IMPOSSIBILITY of the CONTRADICTORY
I know that I exist, think, perceive, and emote – have emotions.
I know I feel because it's part of sensory perception.
I know I desire and will to do things because those are parts of emotion.
But I don't know I exist as what I think I am. I may be a brain in a vat.
I don't know my thoughts are correct. I only know that I think.
I know I'm perceiving a sensation, but I don't know if that sensation is caused by what I think is causing it.
If I think I'm feeling an emotion, I can't possibly be wrong. But I may be wrong about what is causing that emotion.
2. INCONCEIVABILITY of the CONTRADICTORY
This could be called EPISTEMOLOGICAL CERTAINTY or undeniability or rational knowledge.
I know there is no such thing as a square circle because I can't think the concept.
Examples of self stultification:
|By the strictest definition of certainty, impossibility of the contradictory would be the only thing in the category. But we all use the terms "certain" and "know" when talking about things in the category of inconceivability of the contradictory. So because of language convention and practical necessity, we put inconceivability of the contradictory in the category of certainty. And we keep getting sloppier...|
(subject to error, less than 100% certitude)
(a difference that makes no difference)
4. IMPERCEIVABILITY of the CONTRADICTORY
Russell's teapot does not exist.
5. IGNORANCE of the CONTRADICTORY
They may exist, but I have never perceived any evidence of it.
It may not have, but I have never perceived any evidence to the contradictory.
6. IMPROBABILITY of the CONTRADICTORY
I know there have been no alien spacemen land on Earth.
I know magic doesn't exist despite having seen tricks I can't explain.
49% certitude of X is 51% certitude of not-X.
By whatever level of certitude you claim to know that X is true, you claim to know that any hypothesis contradictory to X is false.
|Our language has a problem expressing probability in terms of a percentage. We can legitimately say "1% probable" or "99% probable," but "100% probable" means certain. Yet "100% certainty" is redundant, because certainty has no degrees, so "99% certain" is technically incorrect. We could call it "99% certitude," unless someone wants to quibble that certitude means the same as certainty. Note how disgustingly imprecise our language is for describing philosophical reality! Earthly languages were not designed for correctness; they evolved to get people what they want. And we must all condescend to erroneous conventions in order to communicate.|
Any proposition which violates the laws of logic is necessarily untrue.
I sometimes have thoughts that violate the laws of logic. Therefore, I know that my knowledge is limited, and my thoughts are not always correct.
If I'm not certain of the truth of premises A and/or B, but I am certain of logic, then if A & B logically imply conclusion C, then I am certain that A & B imply C. But I have only the same level of certainty of conclusion C as I have of A & B.