A second tenet holds that this construction of knowledge is developmental, and thus the thinking of the young child is qualitatively different from that of older children and adults. Children do not imitate adult models, but rather construct their own ideas about phenomena. For example, at an early age most children think the moon follows them as they walk. They transform these earlier ideas by inventing and coordinating a series of wrong ideas, with each wrong idea being a constituent part of the next idea. The third tenet holds that all knowledge to be constructed can be classified into one of three kinds of knowledge that differs according to its source and the means by which it is constructed.
Physical knowledge is the knowledge of objects that exist in the external world.
Its source is the object and is discovered as the learner acts on the object. Logical-mathematical knowledge consists of relationships that are invented in the mind of the learner. Relationships of sameness and difference are constructed through the learners' mental actions. Social-conventional knowledge consists of information that is made by people, such as language, morals, and rules. This kind of knowledge is arbitrary in nature and is constructed through social interaction with the cultural group.