“How do you know, that you do not know your self? Your direct insight tells you that yourself you know first, for nothing exists to you without your being there to experience its existence. You imagine you do not know your self, because you cannot describe your self. You can always say: ‘I know that I am’ and you will refuse as untrue the statement: ‘I am not’. But whatever can be described cannot be your self, and what you are cannot be described. You can only know your self by being yourself without any attempt at self-definition and self-description. Once you have understood that you are nothing perceivable or conceivable, that whatever appears in the field of consciousness cannot be your self, you will apply yourself to the eradication of all self-identification, as the only way that can take you to a deeper realisation of your self. You literally progress by rejection — a veritable rocket. To know that you are neither in the body nor in the mind, though aware of both, is already self-knowledge.”
(Source: I Am That, 99. The Perceived can not be the Perceiver)
Know Thyself 