 Modern idealists believe that the mind and its thoughts are the only true things that exist.This is the reverse of what is sometimes called classical idealism or, somewhat confusingly, Platonic idealism due to the influence of Plato's theory of forms (εἶδος "eidos" or ἰδέα "idea") which were not products of our thinking.The material world is ephemeral, but a perfect triangle or "beauty" is eternal.