There are two great tragedies in life: one is to fail to achieve one's grandest ambitions, and the other one is to succeed.

The best simpleminded test of expertise in a particular area is an ability to win money in a series of bets on future occurrences in that area.

The absence of a focal enemy, which is what the Cold War had provided; the complexity of the developments that are occurring that mean that the world is just extremely complicated - lots of different and competing stories and strands; the continuing reality of megaterrorism; and the dysfunctionality of our politics that has neglected the foundations of the U.S. role in the world; have altogether left us somewhat confused.

Terrorism is really the only existential threat to America as we know it - as a free country that plays a leading role in the world.

For interests that are vital to the U.S. - that is, essential for our survival and wellbeing - the U.S. should be prepared to use military force - including unilaterally, if necessary.

Putin needs to understand and feel in his gut that if the Chechens get a nuclear bomb, they're going to Moscow first, they're not coming to New York.

When a rapidly rising power rivals an established ruling power, trouble ensues. In 11 of 15 cases in which this has occurred in the past 500 years, the result was war. The great Greek historian Thucydides identified these structural stresses as the primary cause of the war between Athens and Sparta in ancient Greece. In his oft-quoted insight, "It was the rise of Athens and the fear that this inspired in Sparta that made war inevitable."