Lucilius, my much esteemed friend--While a great gulf separates 1 philosophy from the other learned arts, there is to my mind an equally wide gulf in philosophy itself between the portion which relates to human conduct and that which deals with the nature and power of heaven. The latter is more exalted and more speculative, it allows itself wide liberty. It is not satisfied with mere observation, it surmises that there is a greater and fairer realm placed by nature beyond human sight. Between these two divisions of philosophy, in short, there is as wide a gulf as between their subjects, God and man. The one teaches us what should be done on earth;[25] the other, what 2 is done in heaven. The one dispels our errors and flashes a light by which to thread the mazes of life; the other far transcends this gloom in which we grope, rescues us from the darkness, and leads us to the very source of light itself. For myself, I am grateful to nature, not so much when I see her on the side that is open to the world, as when I am permitted to enter her shrine. Then one may seek to know of what stuff the universe is made, who is its author or guardian, what is the nature of God. Is He wholly absorbed in Himself, or does He sometimes regard us? does He do something daily, or has He done once for all? is He a portion of the world, or the whole world? may He issue new decrees even to-day and thus modify the laws of fate, or is it an infringement of His majesty and an acknowledgment of error to alter what has once been made? for surely the same must always please Him who can be 3 pleased only with what is best. Nor yet withal is His freedom or power diminished, for He is a law unto Himself. [25] In other words, the principles of human conduct.