There are cycles in American politics. US cycles are even more pronounced because we Americans have a totally entrepreneurial presidential system. We don't have parliamentary opposition parties with a shadow prime minister and shadow cabinets. Every four years, the opposition reinvents itself.

Science has everything to say about what is possible. Science has nothing to say about what is permissible.

This week, Iranian-backed Houthi rebels seized control of the Yemeni government, heretofore pro-American. In September, they overran Sanaa, the capital. On Tuesday, they seized the presidential palace. On Thursday, they forced the president to resign.

The great divide in American foreign policy thinking is between those who believe in paper and those who believe in power.

Washington is the only place in the world where a gaffe is when a politician accidently speaks the truth.

Life and consciousness are the two great mysteries. Actually, their substrates are the inanimate. And how do you get from neurons shooting around in the brain to the thought that pops up in your head and mine? There's something deeply mysterious about that. And if you're not struck by the mystery, I think you haven't thought about it.

Great leaders are willing to retire unloved and unpopular as the price for great exertion.