This thesis aims to analyze the role of plasticity in Raízes do Brasil, book debut of Sérgio Buarque de Holanda. For both, it is necessary to evaluate the Portuguese adventitious plastic nature in relation to other elements of Iberian heritage – elements that make up the Brazilian traditionalism, that is, resist the emergence of traces of modern rationalism. As a parameter for the definition of what is modern, the work of Max Weber can be useful for reporting a negative example of Iberian heritage, the innerworld asceticism of the Protestantism puritanical sects. This reference allows theoretical object, on the one hand, an ethic of conquest of the world animated by Protestants religious values and, on the other hand, an ethic of adaptation or adjustment to the world, a position consistent with the plastic nature of Portuguese. Thus, outline a panorama of plasticity that, at the same time which allows the permanence of atavistic elements in our society, makes the success of the Portuguese colonization.