I argue that any binary definition for knowledge (where something is either not known, or known with absolute certainty) is unsatisfactory. This covers all definitions I have seen. I argue that any binary definition that does not require absolute certainty will have a Gettier-type counterexample, exploiting whatever area is left unverified.
Yet, any definitions that do require absolute certainty will find certainty impossible to fulfil, thus all statements will be unknown, making the definition useless.
This could be reworded succintly as: Nothing can be determined with absolute certainty. The degree of certainty required for beliefs to be considered knowledge could be set as not absolute certainty, resulting in knowledge that could be wrong, which is unacceptable. Or, it could be set as absolute certainty, and nothing can ever be known, which is unacceptable.
Unfortunately, the way the concept of knowledge is used in language requires that its definition be binary, that knowledge be absolutely certain. It is impossible to say that "Person A knows Statement X is true" while Statement X has a chance of being false. This means that any attempts to define knowledge while conforming to its linguistic use must fail.