From the Notebooks
Know thyself. This injunction was printed above Delphi's door. It's a command that has exercised seekers throughout the ages. The inscription was a guiding principle for Socrates, Philo, Plotinus (the neo-Platonist author who heavily influenced St. Augustine), and the unknown author of the Theologica Germanica.
This command is crucial. Anyone who dismisses it as a commonplace is dismissing the cornerstone of wisdom. Self-knowledge is the key to understanding your existence, your relationship to others, and your relation to God. All the saints were intensely self-aware–and shed purifying tears at what they discovered.