What are the motifs in Citizen of the Galaxy by Robert A. Heinlein?

Education is a recurring idea. Thorby's growth and transformation (nearly universally for the better) is a direct result of the education he has received. When Thorby goes to live Baslim, the old man observes that his "interest in matters intellectual approached zero" Baslim feels he cannot begin to explain abstract concepts, such as ethics, to Thorby. However, when Thorby leaves Jubbul several years later he is well read, quick-witted, intellectually curious, and fluent in seven languages. Dr. Mader is highly impressed (and surprised) to find these qualities in a former slave and beggar.