Steve Bannon is Donald Trump’s favorite philosopher. Trump sometimes jokes that he doesn't know “whether Bannon is alt-right or alt-left,” but either way Bannon has given voice to the visceral impulse of populist nationalism that Donald Trump has expressed for decades. So what does Bannon believe? A pillar of his worldview is contained in a school of history called Strauss-Howe generational theory, developed by William Strauss and Neil Howe, which states that human events can be loosely organized in terms of recurring eighty year cycles, or saecula, which unfold in four twenty year turnings.