When the self tries to become "pure" by casting out all non-self, its nature and identity becomes obscure. Descartes found the right symbolism for this residual self which knows nothing except its own existence. The last sixteen years of Rousseau's life were one great effort to attain this state of pure selfhood where "time stands still" and the fuga temporum becomes mythical durée. Samuel Beckett pierces Rousseau's last illusions: what is left when a self reaches its "pure" state is not the "eternal moment" of bliss but hopeless suffering just this side of non-existence, and loss of all certainty except the certainty that this consciousness must go on moving without end. Time has become the "eternity" of unwanted existence, an invisible prison without walls and without exit.