Irritatus of Bonisagus creates a box of twelve pieces of wood fixed together with nails.
He removes a splinter from the box, and fixes it as an Arcane Connection to the box.
He casts a spell to detect the box. It works.
He replaces one of the pieces of wood, saving the piece of wood he removed. He casts the spell again.
What happens?
He repeats the procedure eleven further times.
What happens when he casts the spell after each replacement?
He takes the twelve pieces of wood he saved and assembles them into a box.
Which box does his spell detect?
This is, as many people will have noticed, a simplified version of the Ship of Theseus. Philosophers have been arguing over the right answers to the questions above (phrased as "when does it stop being the same ship?") for thousands of years, and have yet to reach an agreement.
Because Hermetic magic is built around Aristotelian metaphysics, it is capable of providing a decisive empirical answer to this question. (It stops being the same box, or ship, when the AC stops working.)
This sort of issue is why there are areas of Hermetic magic where I choose to be vague. What is the boundary of an Individual? Is a suit of armour an Individual or a Group? What is the precise line for something to be inside a Structure? This is a game. If I could solve philosophical problems that have stumped everyone for millennia — actually, I'd probably still make more money managing Ars Magica.