About as much as anyone can count on mathematics, remember history, envision photography, explore science, warm up to cooking, dive into swimming, or ponder psychology.
I once attended an eight week series of lectures by a Seventh Day Adventist archaeiologist talking about archaeology in the Bible. Nice bloke. Clever too. And if the lectures went far away from archaeology they were interesting and I enjoyed them. He was a good speaker.
On the first night he told me, "I'll come and visit you." I hadn't invited him but I didn't say he couldn't come either but when he arrived I couldn't get rid of him.
The second time he came he made a tactical error. He said, "I can only stay for a few minutes. I have an appointment." So every time he tried to leave I asked him a question. He fairly ran to the car when I let him go but after that we understood each other and he didn't outstay his welcome.
I loaned him an introduction to astronomy and when he left the district at the end of his lecture series he took it with him. I didn't mind because I was able to tell a story about a thieving evangelist who stole my book. I got lots of mileage out of that. And then, about five years later, we arrived home in the middle of a rainstorm and found him, sopping wet. huddled on my patio. He had brought it back. Darn it! He spoiled a good story.
Randy D 