After conducting 31 “cross-examination”-style public interviews of presidential historians and White House insiders, attorney Talmage Boston believes he has identified 10 key traits of successful presidents.

Boston shares those traits in the book Cross-Examining History, and he discussed them during a speech for the John Locke Foundation and the Triangle Lawyers Chapter of the Federalist Society. In the video clip below, Boston shares one key trait of his favorite president, Abraham Lincoln.

6 p.m. update: Click play below to watch the full presentation.