任何無矛盾嘅形式系統，只要蘊涵Peano算術公理，就可以喺入面整啲唔能夠被證明或者否證嘅命題，亦即係話，個系統係唔完備嘅。
Any formal system without contradictions, as long as it contains Peano's axiom of arithmetic, can contain a single proposition that cannot be proved or denied, that is, the system is incomplete.