William Duiker is a former history teacher at Penn State University and a former United States Foreign Service officer. Duiker has publically disagreed with Friedman's theories of globalization saying that economic unity has little bering on globalization.
Thomas Friedman's theory of globalization states that two countries with a business relationship are less likely to go to war because they are part of the same global supply chain. These chains affect government policy, and therefore keep a country from taking aggressive steps towards war.
Duiker counters that these supply chains do not guarentee peace because of simultanious fragmentation. Although economic bonds between nations can create unity, they can also increase competition for resources and lead to aggressive or protective economic policies that will result in equally aggressive government policies.