What is the theme in Out of the Silent Planet by C. S. Lewis?

There are many interesting themes to this story. Lewis's fictional books are primarily Christian allegories. We see Lewis's Christian values come out. Earth, a planet that has failed to recognize God remains silent. Man has been seduced by dark forces: he is addicted to insatiable greed and desire instead of looking to a benevolent light. We see what can be when different cultures and species live under one benevolent God like they do on Malacandra. Divine's greed to exploit other planets is a critique on colonialism: especially the British kind.