In the 17th chapter the old rebbe the old rebbe asks a question: it says in the Torah that it is very close for a person to do the Torah in his heart, meaning, it is easy to love G-d. But it is very hard to turn his heart from desiring the things in the world, and to love G-d instead? The old rebbe answers: every person can think whatever he wants, since he has a brain. And therefore he can easily think about the greatness of G-d, and then he will love G-d.