From Section 21 of the Xunzi, Burton Watson’s translation:
The thing that all men should fear is that they will become obsessed by a small corner of truth and fail to comprehend its overall principles. . . . Nowadays the feudal lords follow different theories of government and the philosophers of the hundred schools teach different doctrines. Inevitably some teach what is right and some, what is wrong; some rulers govern well and others bring about disorder. Even the ruler of a chaotic state or the follower of a pernicious doctrine will undoubtedly in all sincerity seek what is proper and try to better his condition. But he is jealous and mistaken in his understanding of the Way and hence allows other men to lead him astray. He clings to his familiar ways and is loath to hear them spoken ill of; he judges everything on the basis of his old prejudices; and when he encounters some different theory, he is loath to hear it praised. Thus he moves farther and farther away from a condition of order, and yet never ceases to believe that he is doing right. Is this not what it means to be obsessed by a small corner of truth and to fail in the search for proper ways? If one fails to use his mind, then black and white may be right before his eyes and he will not see them; thunder or drums may be sounding in his ear and he will not hear them. How much more so with a man whose mind is obsessed!
Or, as Nietzsche put it, “A very popular error: having the courage of one’s convictions; rather it is a matter of having the courage for an attack on one’s convictions!!!” Xunzi goes on to list various ancient Chinese philosophers who exemplified different types of blinding obsession (the primary meaning of 蔽 is to screen or conceal) — all of which are still very much with us. The specific names he lists may mean little to most of us (Mozi and Zhuangzi are the only ones with whose thought I can pretend any familiarity), but the obsessions which they represent, and which Xunzi so neatly encapsulates, are perennial.
Among the itinerant philosophers of former times there were men who were obsessed; the followers of pernicious doctrines are an example. Mozi was obsessed by utilitarian considerations and did not understand the beauties of form. Songzi was obsessed by the need to lessen desires, for he did not understand how they could be satisfied. Shenzi was obsessed with the concept of law and did not understand the part to be played by worthy men. Shen Buhai was obsessed by the power of circumstance and did not understand the role of human intelligence. Huizi was obsessed by words and did not understand the truth that lies behind them. Zhuangzi was obsessed by thoughts of Heaven [i.e., Nature] and did not understand the importance of man. He who thinks only of utilitarian concerns will take the Way to be wholly a matter of material profit. He who thinks only of desires will take the Way to be wholly a matter of physical satisfaction. He who thinks only of law will take the Way to be wholly a matter of policy. He who thinks only of circumstance will take the Way to be wholly a matter of expedience. He who thinks only of words will take the Way to be wholly a matter of logic. He who thinks only of Heaven will take the Way to be wholly a matter of harmonizing with natural forces. These various doctrines comprehend only one small corner of the Way, but the true Way must embody constant principles and be capable of embracing all changes. A single corner of it will not suffice. These men with their limited understanding saw only one corner of the Way and, failing to understand that it was only a corner, they considered it sufficient and proceeded to expound it in engaging terms. Such men bring chaos to themselves and delusion to others.