Why did Plato believe that perfect equality cannot be found in the visible world?

Plato argued that perfect equality cannot be found in the visible world because sensible particulars are inherently imperfect and subject to change.12

In his theory of forms, Plato posited that while humans possess a clear concept of equality, any attempt to identify it in physical objects—such as two pieces of wood—fails upon close inspection. A detailed visual examination of such objects always reveals slight disparities or imperfections, meaning they are never truly equal in an absolute sense.2

Because sensible particulars exhibit the phenomenon of "rolling around between being and not-being," they cannot serve as the source of our knowledge of perfect concepts. Instead, Plato concluded that these concepts, including equality, are abstract objects that exist as eternal, unchanging forms accessible only to the mind, rather than the senses. Consequently, our knowledge of perfect equality must be recollected by the soul from an existence prior to our sensory experience.132