William James

The American original who made philosophy actually useful. James was a medical doctor turned psychologist turned philosopher who basically said: stop arguing about what's 'true' in some abstract sense - does it WORK? That's pragmatism in a nutshell. He wrote 'The Principles of Psychology,' a 1,200-page masterpiece that's still readable (rare for philosophy), and coined the term 'stream of consciousness.' He struggled with depression his whole life but turned that struggle into insight about the power of choice and belief. His 'will to believe' argument? Sometimes you have to believe something works before it actually works - self-fulfilling prophecy as philosophy. He also dabbled in psychic research because why not? The man was curious about EVERYTHING.