Professor chang has spent years studying human history and social change and developed an abstract, systematic model that explains how as countries become wealthier their cultures shift to become more tolerant and open. this would be an example of

a Theory

Explanation:

A theory is an initial explanation to an event/occurrence  which is made based on an educated guess that can be considered as 'scientifically plausible' . (This means that we can't really hold a theory as fact since it hasn't been scientifically proven. )

The excerpt above fill all requirements of a theory:

1. It tried to explain a certain occurrence (how countries become wealthier their cultures shift to become more tolerant and open )

2. It is an educated guess (It is mentioned that Professor Chang has spent years studying human history and social change , this means that he had at least some level of expertise regarding the subject)

3. But it has not been really proven yet, since Professor Chang hasn't develop a scientific research to test the theory.

i claim you tobemy lord