Since man is not omniscient, a definition cannot be changelessly absolute,
because it cannot establish the relationship of a given group of existents to
everything else in the universe, including the undiscovered and unknown. And
for the very same reasons, a definition is false and worthless if it is not
contextually absolute—if it does not specify the known relationships among
existents (in terms of the known essential characteristics) or if it
contradicts the known (by omission or evasion).