"I've been thinking about writing a novel."
"I don't understand."
"I said, I've been thinking about writing a novel. What's there not to understand?"
"The phrase thinking about writing. Is that even grammatical? And if so, what could it possibly mean?"
"What? It's perfectly gram—oh, I get it. Fine. No hedging: I am going to write a novel!"
"Sorry, I still don't get it. I know what it means to have written something, or to be at a keyboard writing something. But to be going to write something, in the unobservable future? Even if the concept is coherent—and I'm not sure it is—how could you possibly know?"