Changes in society are due chiefly to the development of the internal contradictions in society, that is, the contradiction between the productive forces and the relations of production, the contradiction between classes and the contradiction between the old and the new; it is the development of these contradictions that pushes society forward and gives the impetu6 for the suppression of the old society by the new.
Mao ZedongSome people have read a few Marxist books and think themselves quite learned but what they have read has not penetrated, has not struck root in their minds, so that they do not know how to use it and their class feelings remain as of old. Others are very conceited and having learned some book-phrases, think them terrific and are very cocky; but whenever a storm blows up, they take a stand very different from that of the workers and the majority of the peasants. They waver while the latter stand firm, they equivocate while the latter are forthright.
Mao Zedong