Selective Knowledge

This afternoon The Pastor, our son, and I all went to Wal-mart to do some grocery shopping. On the way home, a truck was driving in front of us that had a sticker on the rear window that said, "Real trucks don't have spark plugs."

"What does that mean?" I asked "Don't all cars need spark plugs to run?"

The Pastor told me that the truck was a diesel and diesel engines don't use spark plugs. He then launched into a 15 minute explanation of engines; how they work, the difference between gas and diesel, spark plugs, glow plugs, on and on... He went on to explain compression ratios and ignition source and finally finished up with the difference between regular gas and premium gas and which kind you'd want to use in which kind of cars and why.

I looked at him dumbfounded as he beamed with pride at his vast car-guy knowledge. After a minute or two of silence I finally asked him the question that had been plaguing my mind while he spoke...

"How can you know all that and not know how to work the remote for the TV?"