Engineers think that equations approximate the real world.
Scientists think that the real world approximates equations.
Mathematicians are unable to make the connection. A Mathematician, a Biologist and a Physicist are sitting in a street cafe watching people going in and coming out of the house on the other side of the street. First they see two people going into the house. After a while they notice three persons coming out of the house. Three engineering students were gathered together discussing the possible designers of the human body.