Deficient egotism is nearly as injurious to belief as exaggerated egotism. Everyone knows that those who have led the strictest lives — who have suppressed natural emotions the greatest — if they do go wrong, go with a force and irresistible swing which makes the habitual sinner stare. The **stock instance** is the sons of clergymen, who, brought up more stoically than other people, are said to be the most apt to succumb to the temptations of an uncontrolled life. Nuns, who have submitted for years to oppressive conditions in a convent, occasionally break loose and then fly to the utmost extreme of wickedness. A young man sowing his wild oats is one who has been brought up under restrictive methods, and has suddenly secured his freedom.

(Notice "Everyone knows" in the second sentence, and "stock instance" in the third.)


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Note added at 5 hrs (2017-05-10 15:47:04 GMT)
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I really like Robert Forstag's suggestion of "ejemplos archiconocidos."