Lecture II

When we turn our attention from the act of seeing to that activity which may be seen externally through the movement of the arms and hands, we immerse ourselves in an element that is very difficult to grasp consciously. Even so, we can follow what takes place in our life of feeling when we gesture with our arms and hands, which are free for this kind of activity, and we can become aware of the way this action is related to depth perception with our two eyes. What is it really that depth perception mediates to us? It is the exact position of the left and the right eye. It is the convergence of the left axis and right axis of sight. The mental judgment of the distance of some object from us depends upon the distance at which the lines of sight cross each other. Very little of this convergence activity of the eyes lying at the basis of the judgment of depth is outwardly perceptible.