Find the paradox to solve a problem

From Marty Neurmeir in Dreaming: A Metaskill for the Future (Rotman Spring 2014):

"If you can describe the central contradiction within a given problem, you are well on the way to solving it.  When designer Mitchell Mauk noticed a problem with the storm drains in San Francisco, he took the initiative to propose a solution.  The city had been concerned about people dumping motor oil and chemicals this  into the sewers, where they would flow into the bay and pollute the fish habitats.  The usual warnings posted near the drains weren't working.  In this case, the central contradiction might have been stated like this: people won't stop dumping toxins through the sewer grates unless they can read the signs, and they won't read the signs if they're too busy dumping toxins through the sewer grates.  So Mauk asked the question another way: Can the sewer grates and the signs be one and the same?  He quickly imagined a grate in the shape of a fish.  His elegant Gratefish now sends an unambiguous message: whatever you put down this drain goes right into the fish."