scratch

§ Proof of Godel Incompleteness from Turing Machines

created 2026-04-12
  • Suppose theory T is complete and consistent.
  • Then T gives us a halting oracle, since T 'knows' whether a turing machine M halts or does not halt.
  • The idea is that when we are given a TM M and an input x, we can write down the statment "M halts on input x" as an arithmetic statement and then ask T whether this statement is true or false.
  • This gives us contradiction, as halting oracle cannot exist via halting problem reduction.
❦
Newer ৪ Blog ৪ Older