Berkeley was a friendly guy who limited his battles to speculative philosophy. Tell him that his mother is so fat that she sat on an iPhone and turned it into an iPad, and he'll laugh and slap you on the back. But suggest that maybe there is a material substratum that supports perceivable qualities, and you will be drowned in a torrent of furious arguments.

Berkeley made one exception to this rule when he delivered a series of sermons on the topic of "passive obedience." Big mistake. Yes, there was a philosophical point of sorts there—namely, that the king has a divine right to rule and thus should always be obeyed. But no one missed the political message, which seemed to indicate support for the deposed King James II of England.

Berkeley was thereafter branded a "Jacobite," a radical supporter of rebellion against the government. He explicitly denied holding this view, but the charge stuck. As a result, his advancement in the Anglican Church was blocked for many years.

After that, Berkeley learned to stay out of politics. From then on, whenever someone asked him for his political views, he would simply smile and tell him a joke about how fat his mother was.