The symbol, usually in the form of a circle, of a snake (or dragon) eating its tail.
--The Oxford English Dictionary, Second Edition
The snake eats its tail until it disappears:
"There's no such thing as absolute truth."
"What is true for you is not true for me"
"I have the right to choose whatever morality I prefer."
"My brother is an only child."
"I don't speak a word of English."