One can never reach true self-knowledge without having come to a knowledge of the world. To brood over our inner self will not lead to self-knowledge. What prepares the self for self-knowledge is world knowledge. In turn, one cannot come to a world knowledge without having first delved into his own self. Knowledge of the world is impossible without self-knowledge.
The two statements may seem contradictory, but it is a lively and fruitful contradiction: we cannot come to a knowledge of the world without self-knowledge, neither can we attain self-knowledge without a knowledge of the world. It is like the beating of a pendulum which must swing back and forth. So must man constantly search for the pendulum that beats, now between self-experience and world experience, and now between world experience and self-experience. This inner activity will bring about a strengthening of the soul. It is today a soul necessity and will be more so in the future.
Source (German): Rudolf Steiner – GA 192 – Geisteswissenschaftliche Behandlung sozialer und pädagogischer Fragen – Stuttgart, 1 May 1919 (page 71)