This note is a part of my Zettelkasten. What is below might not be complete or accurate. It
is also likely to change often.
Strange loops are self-referencing ideas which are often paradoxes. Strange loops can be seen in the music of Bach (Cannons, and their casual cousin the Fugue, are self-referencing pieces of music). These loops can also be seen in the designs of Escher (Endless staircase and the infinite waterfall). These strange loops have been observed in maths/logic too. Read more.
A formal system consists of just two things: Read more.