In order from most abstract to least abstract, the levels of theory abstraction are:

The levels of theory abstraction represent a hierarchy of complexity and specificity in theoretical frameworks. At the highest level of abstraction, grand theories provide broad, overarching ideas that encompass various aspects of a discipline but often lack specific testable propositions. They aim to explain large-scale phenomena and offer a wide-ranging perspective.

Following grand theories are conceptual models, which while still abstract, tend to provide a more focused framework for understanding specific concepts or processes. They bridge the gap between broad theoretical ideas and more empirical or practical applications, offering a visual or structural representation that can help elucidate relationships between various concepts.

The least abstract level is occupied by middle range theories, which are more specific and directly applicable to particular situations or sets of phenomena. These theories are designed to be directly testable and provide insights that can inform practice or further research.

This hierarchy of abstraction goes from grand theory, which is the most abstract, to conceptual models, and finally down to middle range theories, which are the least abstract because they deal with specific, concrete issues.

Thus, the correct order from most abstract to least abstract is grand theory, followed by conceptual model, and then middle range theory.