My favorite post-classical educational philosopher is John of Salisbury. He was a 12th century English scholar and statesman. John was the secretary of two successive archbishops of Canterbury (Theobald and Becket), and a noted author. He wrote a biography of Becket, and he wrote two more famous works: one on politics, Policraticus, and one on education, Metalogicon.
John was a staunch defender of the artes liberales (the liberal arts, or the arts which have the power to free the human soul). One of my favorite quotes from the Metalogicon is:
The liberal arts are said to have become so efficacious among our ancestors, who studied them diligently, that they enabled them to comprehend everything they read, elevated their understanding to all things, and empowered them to cut through the knots of all problems possible of solution.
This, to me, is the true measure of a great education. Those who are truly educated have the tools to analyze and acquire new information and understanding. A strong liberal arts background equips one with those tools.
For those who are regular readers, I've started reading the collected works of Thomas Jefferson. So expect quotes and thoughts from one of my favorite Americans to be coming soon!