Nephrite as a surface treatment. A lot of nephrite tools and amulets are known since the Early Neolithic (VII mill. BC) to the Late Chalcolithic (V mill. BC) on the Balkans (mainly Bulgaria; also in Greece, Serbia, Croatia) from two or more unknown sources - Balkan "nephrite culture". Such tools are found in the Later Neolithic of Poland (from the most probable local source Jordanów), Sardinia (Italy) (unknown source) and Switzerland (Kostov, 2005; 2013). Single or just a few finds of nephrite artifacts are reported also from some other European countries. During Neolithic times, the key known sources of nephrite jade
Theory of forms and the theory itself is not developed. Similarly, in the Republic, Plato relies on the concept of Forms as the basis of many of his arguments but feels no need to argue for the validity of the theory itself or to explain precisely what Forms are. Commentators have been left with the task of explaining what Forms are and how visible objects participate in them, and there has been no shortage of disagreement. Some scholars advance the view that Forms are paradigms, perfect examples on which the imperfect world is modeled. Others interpret Forms as universals, so that the Form