Meinong
He then criticizes Meinong's theory of objects which, according to Russell, is ontologically promiscuous and self-contradictory. Both of these criticisms stem from Meinong's theory that there is an object, whether it exists or subsists, for every set of properties. Therefore there is an object that is both round and not round, or round and square. Russell argues that Meinong's theory entails conclusions such as "the present King of France" both exists and does not exist. However, Meinong does not attribute existence (or any other sort of being) to non-existent objects. Russell also accuses Meinong of violating the law of non-contradiction by asserting that the "round square" is both round and not round. Meinong, on the other hand, maintains that the laws of logic do not apply to such phenomena as "impossible" objects that have no being.
Read more about this topic: On Denoting