The opponents of the Chassidic movement once asked the Alter Rebbe, Rabbi Schneur Zalman of Liadi, what he had accomplished with his new path in Divine service.  After all, they – the misnagdim – do not learn Chassidus, but they serve G-d.

The Alter Rebbe responded that the very same question had been posed to his grandfather – the Baal Shem Tov – Why had he made a new path in serving G-d? There are numerous works of Mussar; and there are great tzaddikim such as the author of the Reishis Chochmah, and the Shaloh HaKadosh, and many more. So why does he – the Baal Shem Tov – institute a new path?

Grandfather – recounted the Alter Rebbe – responded with a parable.

Every homeowner has a yard with various buildings: a home for the family; sheep pens; a building for storing produce. Al l of these must be guarded from thieves.

When it comes to protecting property from thieves, there are two ways to do so. One way, is that as soon as the owner spots the thief, he begins yelling, and the thief runs away. The second way is that the homeowner catches the thief, brings him into his home, and begins the process of education.

Such – recounted the Alter Rebbe – was the response of grandfather.

There is an advantage in the first approach, for the thief immediately runs away; the problem, however, is that as far as the thief runs away, there is always the potential for recidivism. The second approach has the advantage that one begins educating the thief, so that he will never steal again. Yet, in order for this approach to be successful, one must have stamina and wisdom.

In the Baal Shem Tov’s parable, together with the Alter Rebbe’s explanation, there is a clear response to the question regarding the different paths in Divine service: the path of rectifying one’s character through the Mussar approach, as compared to the path of rectifying one’s character with the path of Chassidus.

Both Mussar and Chassidus protect one from theft; yet Mussar cries out, “this is a sin!” When a Jew hears the word, “sin,” he won’t transgress… the thief runs away! Yet, who can be sure that the thief won’t find another way to steal, or sundry excuses and justifications how it may be permissible.

The path of the Baal Shem Tov is that we begin educating the thief. However, in order for this to be successful, we must first think intellectually, and prepare ourselves for a long path.

As well as we prepare ourselves, sometimes the thief wears various fine items of clothing, and we must be very intelligent in order to understand the thief; additionally, one must have stamina to work with the thief, and have a strong heart to withstand the pleading of the thief to let him go.

(Free translation from a talk of Rabbi Y.Y. Schneerson, on the 7th day of Pesach 5696/1936, page 7 here).