Modernization theory and dependency theory are both theories of societal development that address the ways that developed countries became developed and how undeveloped, or underdeveloped, countries may do so themselves. Both theories agree that there are, simultaneously, rich states and poor states and that it is possible for poor states to modernize and become rich states.
Despite these similarities and the fact that both theories look at the venues through which developed countries were once able to modernize, they differ immensely because of their respective assumptions of the role of undeveloped countries in the process of modernization. By assessing not only the process of one state modernizing but also the complex relationship between rich and poor states, dependency theory accomplishes a much more comprehensive and practical understanding of the process of state progress and change.
Modernization theory takes a step-by-step, analytical look at the ways a country may modernize. The theory views things such as corruption and a lack of economic growth to be obstacles to modernization while it views technology and science as necessary for growth as a state. Dependency theory has a more sympathetic understanding of the process of modernization in that it strives to recognize the fact that each country is unique and therefore may not necessarily follow the same rules as other countries in terms of a path towards modernization and success. Primarily, however, the important difference in dependency theory is that it explains that many poor states are poor by virtue of the fact that there are other, more modernized states that have taken advantage of its position and resources.
Dependency theory argues that the modernization of underdeveloped states is not as simple as following the path that developed states have taken because they are in their inferior position in the world market because of that path. To dependency theory, to expect an underdeveloped state to follow suit would be to neglect the complex array of causes for their current position and also to condemn another state to such an inferior position.