A proper theologian must have a Devil

"I did not learn my theology at once, but had to seek ever deeper after it.  That is where my spiritual distress led me;  for one can never understand the Holy Scriptures without experience and tribulations... If we do not have such a Devil, then we are nothing but speculative Theologi, who handle their thoughts badly and speculate about everything with their reason, that it must be like this and like that; just like the way of the monks in the monasteries."  

Luther in Oberman, p.185 (Man between God and the Devil)