Canon: one single theme is played against itself.
Fugue: less rigid canon
The genius of Escher was that he could not only concoct, but actually portray, dozens of half-real, half-mythical worlds, worlds filled with Strange Loops, which he seems to be inviting his viewers to enter.
Epimenides paradox.
All consistent axiomatic formulations of number theory include undecidable propositions.
This statement of number theory does not have any proof in the system of Principia Mathematica.
To derive all of mathematics from logic without contradictions...
lmao