Lecture Two

By imagining the outline of the human being we may arrive at the following concept. Let us assume that the person in the diagram is lifting a weight by hand, in our case a heavy object weighing one kilogram. The object is lifted by hand. Let us now ignore the person and, instead, tie the object (A) to a rope, pass the rope over a pulley, and tie another object of either identical or heavier weight to the other end (B). If B happens to be heavier, it will draw the original weight (A) up. We have here constructed a mechanical device the achievement of which is identical to that of hand and arm. I can replace hand and arm with a mechanical device—the result is the same. I unfold my will and, in so doing, I accomplish something that can equally be achieved by some mechanical device, as shown in the illustration.