Orwell’s four motives for writing still seem to me the most honest account of why long-form non-fiction writers do what they do, with “sheer egoism” at the top; next, “aesthetic enthusiasm” – the pleasure principle or sheer relish of sonority (“pleasure in the impact of one sound on another”); third, the “historical impulse” (the “desire to see things as they are”), and, finally, “political purpose”: the urge to persuade, a communiqué from our convictions.--Simon Schama