I used to think that Descartes was the one writer who created alone in his garret, but it turns out I was wrong about that. It seems that he actually belonged to a collaborative group, as do almost all writers. He met with his friends at coffee houses, prevalent in the Netherlands, where Descartes spent much of his life. It was during those mostly friendly, but often argumentative, meetings that he worked out many of his theories.
There are innumerable examples of writers throughout the ages relying on one another for inspiration. Inspiration is the problem for writers and creative types, not isolation. Well, isolation is one problem, but it's illusory. Writers never have to work alone; they do need to reach out to one another, however.
Think of the Bloomsbury Group in London (inhabited variously by Virginia Woolf, Leonard Woolf, E.M. Forster, and others) , the Inklings, which included C.S. Lewis and J.R.R. Tolkien, in Oxford, and the informal literary group formed by expatriates Hemingway, Fitzgerald, and Gertrude Stein in Paris. These writers came together because they needed to talk to one another, to feel connected, to create new ideas. They stole from one another, and often got into arguments about plagiarism, but plagiarism, for writers, is the fine line between inspiration and innovation. It can be virtually impossible to know for sure who created what, when you work in collaboration. This can be a real problem, but that's for another post.