Okay. I know what you're thinking. What does philosophy have to do with writing? The quick answer is: Everything.
Everything we think and therefore, everything we say or write has some kind of philosophy behind it. (Whether you know anything about philosophy or not.) Chances are, you don't consciously weave philosophy into your writing--few people do--but it's there nonetheless. Ayn Rand did it on purpose, but she's the only one I can think of who did it consciously. Usually philosophy just slides in unnoticed. (And please understand that I am referring to the writing of fiction here. Plenty of non-fiction writers are thinking about the philosophy behind their work.)
For example, if you believe the world is a horrible place and we're powerless to do anything about it, your writing is going to reflect that belief. Or if you believe mankind is heroic, it will show in your work.
Why am I telling you this? It's helpful to know what drives you, so you can write better. If you know where your philosophy lies, you can direct your work. You can write a heroic character and a conversely non-heroic villian. (Or if it's your bag, the other way around.) If you understand the philosophy driving you and therefore your characters, you can create believeable people. You can write a villian who makes your skin crawl, and a hero who makes your pulse race.
It's also helpful to understand that philosophy drives writing, so as a reader you can begin to spot an author's philosophy. Writers like Rand and Dumas wrote heroic pieces. Hemingway had a horrible sense of life, and his work shows it. Joyce... I can't imagine what was going on in his mind, but yuck. And it's not just in the literary genre either. You can actually see a philosophic progression in Michael Crichton's thrillers from one book to the next (and if you'd don't believe me, read his early works and compare them to The State of Fear.)
(More on this later...)
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