Another way of saying this is to state that the only way for a particular compound or function to survive in the long run is for it to be a product of another compound or function. In this circular world all causes are results, just as all knees are laps. Contrary to common sense, all existences depend on the consensual existence of all others. As the reality of the lap game proves, however, circular causality is not impossible. Tautology can hold up 200 pounds of flesh.
Tautology is, in fact, an essential ingredient of stable systems.
As examples, Hofstadter points to the seemingly ever rising notes in a Bach canon, or the endlessly rising steps in an Escher staircase. He also includes as Strange Loops the famous paradox about Cretan liars who say they never lie, and G del's proof of unprovable mathematical axioms. Life and evolution entail the necessary strange loop of circular causality-of being tautological at a fundamental level. You can't get life and open-ended evolution unless you have a system that contains that essential logical inconsistency of circling causes. In complex adapting processes such as life, evolution, and consciousness, prime causes seem to shift, as if they were an optical illusion drawn by Escher.