Through an examination of the development of Multiculturalism and Critical Rationalism, this article intends to expose the commonality amid theories of plural cultures and universal science. Traditionally, the distinction between politics as practice and science as theory has been firmly held, yet by analyzing several philosophers representing separately Multiculturalism and Critical Rationalism, we discover that the interpenetration of theoretical and practical knowledge is rather popular in both the fields of politics and science. With the discovery, we attempt to demonstrate that 'plural cultures' and 'universal science' share a common structure rather than being opposing to each other by referring respectively to their pluralistic and monistic nature.