 Ayers (1974) argued that the concept of a physical object is fundamental to human cognitive processing and that it does provide criteria for counting and persistence even though it is not a sortal since it does not specify an essence. One important part of his argument is the clarification that a physical object is not simply the stuff of spatio-temporally continuous space time region but is a the stuff of a maximal region. That is, we do not generally regard any proper part of a physical object as a physical object.