An inference may be likened to a push given to a wheelchair in which the thinker is sitting. The door of the room is open, and the chair is pointed towards the door. Party A gives the chair a push in the direction of the door; Party B gives the chair another push in the same direction; and Party C then does the same. No one push suffices to get the chair to the door; possibly not all three. In the meantime, Party M gives the chair a push away from the door, and Party N gives another similar push. (…) The movement of the chair at each single push is like an Inference. The final position of the chair is like Proof,-the chair may or may not have reached the door 1 .