Excerpt from Dennis B. Nueunschwander’s BYU Dev. given May 19, 1998:

        As we learn by our experience to distinguish the good from the evil, it is not necessary for us to experience every evil to know that it is evil. The Prophet Joseph asks the question "Why will not man learn wisdom by precept . . . and not be obliged to learn by sad experience everything we know" (Teachings, p. 155).

Brigham Young teaches this principle also as he writes:

        “There is plenty of sin without your sinning. We can have all the experience we need, without sinning ourselves. . . . There is no necessity for such a course, for the world is full of transgression, and
this people need not mingle up with it.”  [JD 3:224]
 

        Do we really need to experience the unhappiness associated with sin before we know that sin causes unhappiness? The answer is an obvious no. We can learn a great deal about evil through our observation of the world around us and through the experience of others.