 The psychologist Xu (1997) has argued that the concept of a physical object is an essential part of cognitive development and is present in infants at a quite early stage. And she argued that physical object is a sortal because there are counting and persistence conditions (Spelke 1990). In contrast to Ayers, she argued that the physical object persists through even fairly dramatic changes, including her Biblical example of Lot’s wife becoming a pillar of salt (Xu 1997). Her position based on her own work and that of others (Xu &amp; Carey 1996, Spelke 1996) is that the acquisition of the physical object concept is a crucial stage in cognitive development and is a step toward the development of the more refined sortal concepts that come with language acquisition. And she agrees with Ayers that the primitive concept remains in the cognitive repertoire of adults and can be deployed in cases where someone is confronted with a physical object whose further characteristics are as yet unknown. A similar argument is presented in Sarnecki (2008) for the necessity of a general sortal for objects as an intermediate step toward the acquisition of the sortals of language.