Rothbard attended Columbia University, where he received a Bachelor of Arts degree in mathematics in 1945 and a PhD in economics in 1956. The delay in receiving his PhD was due in part to conflict with his advisor, Joseph Dorfman, and in part to Arthur Burns’s rejecting his dissertation. Burns was a longtime friend of the Rothbards and their neighbor at their Manhattan apartment building. It was only after Burns went on leave from the Columbia faculty to head President Eisenhower's Council of Economic Advisors that Rothbard's thesis was accepted and he received his doctorate. Rothbard later said that all his fellow students were extreme leftists and that he was one of only two Republicans at Columbia at the time.