The environmment of a child contains other people, usually including a mother, and parts of people including parts of the child itself. Objects often have parts which are objects. However, often only some of the parts are separately identifiable. The boundaries of the parts are often not definite. Some are rigid and some are flexible.
Babies are ready very early to learn what kinds there are.
At least some ternary relations such as betweenness are basic. In its numerical use, it reduces to the equality of two fractions, but the quaternary relation seems to be basic in common sense usage. Many of the objects a child encounters, e.g. lemons, belong to natural kinds . The objects of a natural kind have yet undiscovered properties in common. Animate objects are to be understood in terms of their desires and actions.