What kind of boss hires a thwarted actress for a business-to-business software startup? Stewart Butterfield, Slack’s 42-year-old cofounder and CEO, whose estimated double-digit stake in the company could be worth $300 million or more. He’s the proud holder of an undergraduate degree in philosophy from Canada’s University of Victoria and a master’s degree from Cambridge in philosophy and the history of science.“Studying philosophy taught me two things,” says Butterfield, sitting in his office in San Francisco’s South of Market district, a neighborhood almost entirely dedicated to the cult of coding. “I learned how to write really clearly. I learned how to follow an argument all the way down, which is invaluable in running meetings. And when I studied the history of science, I learned about the ways that everyone believes something is true–like the old notion of some kind of ether in the air propagating gravitational forces–until they realized that it wasn’t true.” —Forbes