How does varying examples in imagination help identify an essence in Husserl’s method?

In Edmund Husserl’s phenomenology, the method of free variation—often referred to as Wesensschau—is central to the eidetic reduction. This process allows a philosopher to move beyond concrete, factual objects to grasp their "eidos," or essential structure.12

The method functions through the following steps:

• Starting Point: The philosopher begins with a concrete object or phenomenon, setting aside (or "bracketing") its actual existence and any contingent, accidental features.12
• Imaginative Variation: The philosopher systematically varies the aspects of the object in the imagination. By mentally altering different features, one tests which characteristics are necessary and which are merely incidental.12
• Identifying the Invariant: As these variations are performed, the philosopher focuses on what remains unchanged throughout the process. The essence is defined as this identical, invariant structure that persists across all possible variations.2

This technique is neither induction nor simple abstraction; rather, it is a way of achieving an immediate intuition of the necessary structure of a thing, independent of factual occurrence.12