Where do correct ideas come from? Do they drop from skies? No. Are they innate in mind? No. They come from social practice and from it alone; they come from three kinds of social practice, the struggle for production, the class struggle, and scientific experiment.
It is man’s social being that determines his thinking.
Man’s knowledge depends mainly on his activity in material production, through which he comes gradually to understand the phenomena, the properties and the laws of nature, and the relations between himself and nature; and through his activity in production also gradually comes to understand, in varying degrees, certain relations that exist between man and man
In class society everyone lives as a member of a particular class, and every kind of thinking, without exception, is stamped with the brand of a class.
Marxists hold that in human society activity in production develops step by step from a lower to a higher level and that consequently man’s knowledge, whether of nature or of society, also develops step by step from a lower to a higher level, that is, from the shallower to the deeper, from the one-sided to the many-sided
Marxists hold that man’s social practice alone is the criterion of the truth of his knowledge of the external world. (Mao Zedong, On practice)
What actually happens is that man’s knowledge is verified only when he achieves the anticipated results in the process of social practice (material production, class struggle or scientific experiment). If a man wants to succeed in his work, that is, to achieve the anticipated results, he must bring his ideas into correspondence with the laws of the objective external world; if they do not correspond, he will fail in his practice. After he fails, he draws his lessons, corrects his ideas to make them correspond to the laws of the external world, and can thus turn failure into success;[...]”
The Marxist philosophy of dialectical materialism has two outstanding characteristics. One is its class nature: it openly avows that dialectical materialism is in the service of the proletariat.(On practice, Mao Zedong)
Here [Oppose book worship] is one of the most inspriring thought from chairman Mao: it includes among others the famous stance No investigation, no right to speak!