The philosopher will fall neither into the cold unfeeling indifference of the recluse nor into the frothy effervescing fussiness of the sentimentalist. He knows that the first attitude is generated by excessive introversion, the second by excessive extroversion. His ideal being the balance between them, he will attend properly to his own self-development but, side by side with it, work helpfully for mankind.
-- Notebooks Category 20: What Is Philosophy? > Chapter 4: Its Realization Beyond Ecstasy > # 213