The “Ship of Theseus” is a philosophical thought experiment that explores identity over time. It poses the question: if a ship has every single one of its original parts replaced over time, is it still the same ship?
Forget about identity.
When we say ‘two things are similar’ we usually relate to the information that our senses give us or the assumptions we have (all steel atoms are exactly the same, or : atoms).
It can be that the reality we experience do not correspond to rules of identity, in other words… it’s an illusion, a practical tool for survival and some other things.
Symmetry
Symmetry can be seen as : Efficiency in growth, structural stability (spherical, radial, bilateral etc’) and physical laws produce symmetries in space gravity, electromagnetism, fluid dynamics, snowflakes, sand ripples, spiral galaxies, soap bubbles – how energy stay minimal, settling into states that needs the least energy.