Editor’s note: Walter Isaacson ’74, a member of the Board of Overseers and biographer of Steve Jobs and others, is writing a book about the great inventors of the digital age. The following is his abridgment of a section on Bill Gates ’77, LL.D. ’07, co-founder of Microsoft, who now runs the Bill & Melinda Gates Foundation. Gates returned to campus for a discussion on philanthropy as part of the campaign launch. For the full version, which was published online then, please go to http://harvardmag.com/gates-13.