Warren was a philosopher and scientist. As a freshman at Haverford College he told the Quaker philosopher Rufus Jones that all he wanted to know was: "What is a number that a man may know it; and a man, that he may know a number?" To this the Quaker famously replied: "Friend, thee will be busy as long as thee lives." Warren acknowledged in his last days that the prophecy had been fulfilled, and...

Philosopher: Today, I suggest we discuss the important concepts of common knowledge and common belief. As far as I know, the first one to give a formal analysis of these concepts was the philosopher David Lewis, in his book Convention [131]. One of his examples is traffic conventions, about the role of common knowledge in how one behaves in road traffic. To explain this properly, I wonder if yo...

Traditional philosophy has been under attack from several quarters in recent years. The traditional philosopher views philosophy as an armchair discipline relying, for the most part, on reason and reflection. Some philosophers doubt the legitimacy of this type of inquiry. Their arguments usually occur along two dimensions. Some argue that the primary data source for the armchair philosopher—int...