The sources establish that the **core principle** of Structural Thinking is that **the underlying structure of anything will determine its behavior**. In this larger context, the concept of "**change of underlying structure will lead to a change of behavior almost invariably**" is presented as a fundamental truth and a key tenet for achieving lasting transformation.

Here's how this concept is discussed:

*   **Direct Consequence of the Core Principle**: If structure determines behavior, then logically, altering that underlying structure is the most effective way to change behavior. The sources state this directly: "**a change of underlying structure will lead to a change of behavior almost invariably**". This emphasizes a strong causal link, suggesting a high degree of predictability and reliability when structural changes are made.
*   **Contrast with Rejected Change Efforts**: This concept stands in stark contrast to other, often unsuccessful, change initiatives. Many well-intentioned efforts, like the quality movement inspired by Deming, are often "rejected by the organization the same way the body rejects an implanted organ". This happens because "**if the underlying structure is not conducive to change no matter what kind of change effort you put in no matter how good it might be... what will happen is the organization itself will reject it**". The critical insight here is that the *quality of the change effort itself* is less important than whether it addresses the fundamental underlying structure.
*   **Explaining Consultant's Frustration**: The principle clarifies why consultants, despite doing their "best work" and achieving initial success, often find that "it's as if it never happened" two years later. This is not due to personal failure but because "**it wasn't an adequate change of underlying structure that would have created sustainability in those changes**". The sources emphasize that this rejection is "not personal," but "structural," likened to "nature" or "physics," because "**structure seeks equilibrium**".
*   **Addressing the "Western Tendency"**: The typical Western approach is to immediately ask, "**how do we change it?**" when faced with a situation. However, Structural Thinking advocates for first asking, "**how do we understand what's giving rise to the predictable patterns of behavior that we're seeing?**". This foundational understanding of the underlying structural dynamics is crucial *before* attempting change, precisely because only a change at this deep level will result in sustainable behavioral shifts.
*   **Shifting Behavioral Patterns**: The underlying structure is responsible for producing two main patterns of behavior: oscillation and resolving advancing structure. When the underlying structure is changed, the intention is to move away from the undesirable oscillating patterns (e.g., build up capacity then downsize, centralize then decentralize) towards a **resolving advancing structure**. This latter structure is outcome-oriented, focusing on clearly defining desired outcomes, understanding the current reality, and then moving effectively from the current state to the desired state. This shift is a direct result of altering the underlying structure.
*   **Tension and Equilibrium**: The dynamic that drives behavior is that "structure seeks equilibrium". **Tension** is defined as "a structure of a contrast between a desired state and an actual state". This non-equilibrium state naturally seeks resolution. A proper creative process, guided by structural thinking, brings the current state up to the desired state, achieving equilibrium. This process of resolving tension by bringing current reality in line with a desired outcome *is* the manifestation of a changed underlying structure leading to new, desired behaviors.

In essence, the sources strongly assert that to achieve durable and meaningful behavioral change, one must identify and modify the underlying structural dynamics, as opposed to merely addressing surface-level problems or implementing temporary solutions.