You can observe a lot just by watching.
You can't expect to hit the jackpot if you don't put a few nickles in the machine.
You can't fall off the floor.
You can't get here from there.
You can't guard against the arbitrary.
You can't outtalk a man who knows what he's talking about.
You can't push a rope.
You can't tell how deep a puddle is until you step into it.
You can't tell which way the train went by looking at the track.
You will remember that you forgot to take out the trash when the garbage truck is two doors away.