February 1, 2009
If you attempt to create a wholly imaginary incident, adventure or situation, you will go astray and the artificiality of the thing will be detectable, but if you found on a fact in your personal experience, it is an acorn, a root, and every created adornment that grows up out of it and spreads its foliage and blossoms to the sun, will seem reality, not inventions. You will not be likely to go astray; your compass of fact is there to keep you on the right course.

Mark Twain’s notebook (1935).

It struck me how well this applies to long-form improv. A scene which is grounded in some truth can spin off into wild places, but a scene with no grounding in truth soon finds itself stalling out on the runway.