If a child occasionally tears the pages out of a book left within his reach, it may be difficult to communicate your desire due to his failure to remember the previous rebuke. It may be confusing to him when he is suddenly disciplined for tearing the pages out of your favorite Bible. But if you place books on the table where he can access them at any time, and you then stand watch closely and prevent him from tearing the pages, the continual reinforcement over one or two days will train him not to tear pages. However, if you allow him to tear up one kind of paper and not another it may be difficult for him to determine what is off limits and what is available for tearing. You the trainer must arrange the environment so as to create the maximum effect in your training.
Consistency is the key.
You cannot allow a child to play with one set of car keys and not pick up other sets he finds lying around. If you want to be assured that he never plays with keys, you must make all keys off limits. This is not done by placing the keys beyond his reach, but by placing keys within his reach and then consistently denying him the pleasure of touching them. A child of any age can be easily trained to play in a room and touch half of the objects and not the other half. As a parent I am not prepared to spend the time it would take to enforce too broad a scope of continual temptation, but there are a few things like books, keys, guns, vases, dishes, etc.