One of my favorite stories recorded in the Sefer Baal Shem Tov (p. 7-8) is about how the Maggid of Mezeritch became a disciple of the Baal Shem Tov:
(Freely translated/adapted): R. Dov Ber began hearing about the greatness of the holy Rabbi, Baal Shem Tov and how people would travel from far and wide to witness and receives his prayers. Now it was that R. Dov Ber had a sharp mind and was an expert in Shas and Posqim. Additionally, he had his hands in the wisdom of the Qabbalah. He was curious as to what made the Baal Shem Tov so great.
He finally decided to travel to the Baal Shem Tov in order to test him. As he was travelling, he began having regrets for R. Dov Ber was unable to learn while travelling, thus distressing him. He finally resolved himself to continue, knowing that he would hear Torah when he arrived to see the Baal Shem Tov. Alas, this was not to be, as all he heard from the Baal Shem Tov were stories. While the stories contain tremendous wisdom, R. Dov Ber did not see the wisdom or depth of the Baal Shem Tov’s words.
R. Dov Ber decided he would return home the following morning. In the middle of the night before his return journey, he was summoned to meet with the Baal Shem Tov.
The Baal Shem Tov asked him, “Do you know how to learn?”
He responded, “Yes.”
The Baal Shem Tov then continued saying, “I also heard that you know how to learn. Tell me, do you have knowledge of the wisdom of the Qabbalah?”
He responded, “Yes.”
The Baal Shem Tov then asked his servant to bring him a copy of the Etz Chaim (Qabbalat HaAri), showed R. Dov Ber one essay and asked him to explain it. R. Dov Ber read over the work and explained the simple explanation of the text.
The Baal Shem Tov said, “You don’t know anything.” So R. Dov Ber went back, looked it over again and told the Baal Shem Tov, “The correct interpretation is like I already stated, so if you think you know a higher explanation, please tell it to me for I will hear truth from whomever shares truth.”
The Baal Shem Tov responded, “Get up for this passage contains names of angels.”
As soon as he said this, the text illuminated the entire house and a fire surrounded them. They sensed the presence of the angels mentioned in the text.
The Baal Shem Tov then said to R. Dov Ber, “In truth the interpretation is as you said however your learning lacks soul.”
At this moment, R. Dov Ber told his servant to return home and he would be staying with the Baal Shem Tov to learn from him great wisdom.
For me, the whole story boils down to one thing, namely that while someone might be intellectually capable of learning and expounding, yet be lacking in soul. To truly reach someone, one must put their whole being, mind, body and soul, into study and teaching.