不同质的矛盾，只有用不同质的方法才能解决。 - Mao Zedong

Criticism and self-criticism is a kind of method. It is a method of resolving contradictions among the people and it is the only method.

What should our policy be towards non-Marxist ideas? As far as unmistakable counter-revolutionaries and saboteurs of the socialist cause are concerned, the matter is easy, we simply deprive them of their freedom of speech. But incorrect ideas among the people are quite a different matter. Will it do to ban such ideas and deny them any opportunity for expression? Certainly not. It is not only futile but very harmful to use crude methods in dealing with ideological questions among the people, with questions about man's mental world. You may ban the expression of wrong ideas, but the ideas will still be there. On the other hand, if correct ideas are pampered in hothouses and never exposed to the elements and immunized against disease, they will not win out against erroneous ones. Therefore, it is only by employing the method of discussion, criticism and reasoning that we can really foster correct ideas and overcome wrong ones, and that we can really settle issues.

我们的宪法规定:中华人民共和国公民有言论、出版、集会、结社、游行、示威、宗教信仰等等自由。我们的宪法又规定:国家机关实行民主集中制，国家机关必须依靠人民群众，国家机关工作人员必须为人民服务。我们的这个社会主义的民主是任何资产阶级国家所不可能有的最广大的民主。我们的专政，叫做工人阶级领导的以工农联盟为基础的人民民主专政。这就表明，在人民内部实行民主制度，而由工人阶级团结全体有公民权的人民，首先是农民，向着反动阶级、反动派和反抗社会主义改造和社会主义建设的分子实行专政。所谓有公民权，在政治方面，就是说有自由和民主的权利。