A set of logically related concepts or statements, which seks to describe and explain development and to predict what kinds of behaviour might occur under certain conditions. A possible explanation for phenomena, used to predict the outcome of research. The way theorists explain development depends in part on the way they view two basic issues: Whether children are active or passive in their own development: john locke a young child is like a blank slate" on which society. Development occurs in a sequence of qualitatively different stages: we now know that both views are too simplistic and both are correct. Each stage involved coping with different problems and developing abilities. Each stage builds on the previous and prepares child for next stage. Most early theoretical pioneers believed in the organismic-stage approach (freud, Mechanistic approach gained popularity in the 60s with the increasing popularity of john: watson"s learning theories.