To experience a mechanical approach, sit on the wing of your car. Your weight makes it sink an inch or two. Isn't that the compression of the air-filled rubber tyre? Well, it is in plain view, so look and see. It has hardly squished at all. To find out where the motion has come from you have to look up inside the wheel arch so that you can see the suspension. Most of the motion has come from a mechanism. Your weight has made a lever pivot about its hinge so that it stretches a spring. There is an important technical reason for car makers taking this expensive mechanical approach, instead of relying on soft materials. The mechanism decouples the different motions. The stiffness of the motion that makes the hinge pivot is determined by the spring. The stiffness of other motions is determined by how solid the hinge is. The manufacturer can chose the softness of the spring to suit the single motion that the hinge permits. The mechanism retains the desired stiffness in other directions independently of the softness of the spring. This is the kind of sophistication one wants of a shoe if it is to measure up to the demands of modern life.