Predicate Calculus does not easily deal with:
Predicate Calculus requires the Law of the Excluded
Middle: if we use a predicate P to represent something,
then either P or ¬ P must be true; ``sort of P'' or ``probably
P'' is excluded as a possibility. The ``real intelligence'' in a
reasoning process may be in the judgment of whether a
proposition is true for a particular case.
- Decomposition of an object into parts: ``A car without an engine''
- Mass nouns: ``five gallons of water''
- Representation at variable levels of detail.
- Meta-rules: ``There's an exception to every rule''
- Things that are usually (but not always)true: ``Most
people can drive a car.''
- Knowledge about the state of knowledge: ``John
thinks Mary believes unicorns exist.''
- Modals: ``You should take your umbrella if it might rain.''