A Theorem with Contradictory Axioms
The USA is a country.
The capital of every country is a beautiful big city
Washington is the capital of the USA, and it's not a big city.
Every big city has crime.
A big city is a city.
Prove there is some city that is beautiful and has no crime.
Then prove there is some city that is beautiful and has crime.
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%----The USA is a country.
fof(usa,axiom,
country(usa) ).
%----The capital of every country is a beautiful big city
fof(country_big_city,axiom,
! [C] :
( country(C)
=> ( big_city(capital_of(C))
& beautiful(capital_of(C)) ) ) ).
%----Washington is the capital of the USA, and it's not a big city.
fof(usa_capital_axiom,axiom,
( capital_of(usa) = washington
& ~ big_city(washington) ) ).
%----Every big city has crime.
fof(crime_axiom,axiom,
! [C] :
( big_city(C)
=> has_crime(C) ) ).
%----A big city is a city.
fof(big_city_city,axiom,
! [C] :
( big_city(C)
=> city(C) ) ).
%----There is some city that is beautiful and has (no) crime.
fof(some_beautiful_crime,conjecture,
? [C] :
( city(C)
& beautiful(C)
& ~ has_crime(C) ) ).
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