Switching between 'Soft' and 'Hard' wrapping in vim

One of the things I sometimes find quite frustrating about vim is that the standard textwidth and wrap options imply assumptions about whether a text-style file (.txt, .md, READMEs, etc.) have “hard” carriage returns (where paragraphs are wrapped with actual carriage returns) or “soft” (where paragraphs are wrapped dynamically by the editor). When you create your own files, you’ll probably have your own preference for which of these you do, but when you are working with files that come from others, it’s very useful to have the ability to quickly switch between them.