Best island to visit in hawaii for Karl MARX used parts of classical theory to develop a socialist economic theory. John Maynard KEYNES, the founder of what has become known as Keynesian economics, stood classical economics on its head. Some modern economists, often known as post-Keynesians, embraced elements of classical economics, while others continued to endorse some aspects of Keynesian thought. Adam Smith (1723 90). Smith’s The Wealth of Nations was a direct attack on mercantilist political and economic practices. As a rule, Smith opposed protectionist policies such as tariffs, but he believed tariffs were legitimate in defense industries. Smith did not support monopolies because he thought they interfered with COMPETITION. Best island to visit in hawaii 2016.