Apparent Motion

When Max Wertheimer described the Phi Phenomenon he was making an important perceptual observation.  His observation of apparent movement created by seeing images in succession embodied the Gestalt principle that 'the whole is greater than the sum of it's parts'. 
This holistic concept not only applies to our vision but also to our other senses.  In all areas of the study of perception it becomes apparent that the input from any of our sense receptors goes through many processes before it becomes something meaningful.  Here is one of my favorite clips that illustrates this concept very well.  Notice how the still images come to life and begin to move as the zeotrope spins.