What is mysticism in Chaim Potok's The Chosen?

In this novel, there is one part in which Reuven’s father
explains Danny’s father’s (Reb Saunders) beliefs to him. Reuven does not understand why
Danny and his father do not talk, why Reb is always silent. David Malter (Reuven’s
father) tries to explain a lot of Jewish history to his son and in one of his “lectures”
he describes Kabbalah, which is Jewish mysticism. Kabbalah is concerned with the
mystical aspect of Rabbinic Judaism. It is a set of mysterious teachings meant to
explain the relationships between God, man and the universe. Kabbalah consists of a set
of scriptures that are considered to be outside the traditional Jewish scriptures. It
seeks to define man’s nature and the nature of the universe, the purpose of existence,
and various other philosophical questions. It presents methods to help people understand
these concepts and arrive at spiritual realization. It uses classical Jewish thought and
sources to explain its teachings. Kabbalists attempt to define the inner meaning of the
Tanakh (Hebrew Bible) and rabbinic teachings as well as to explain the meaning of Jewish
religious observances.

This is illustrated when Danny and
his father engage in their Talmudic discussions that Reuven finds so distasteful and
cruel. Reb Saunders conducts lengthy discussions with his son about the meaning of the
Talmud, but then brings in all sorts of other references. He is testing his son’s
knowledge. He sneaks in “fake” mistakes, hoping his son is astute enough to catch them
and correct them. This is a game they play, which Danny enjoys, but Reuven finds
maddening at first. Eventually, Reuven himself participates, even though his knowledge
is not as extensive as Danny’s.

Also, the way Reb Saunders
has chosen to raise Danny is mystic. He does not talk directly to him. When he wants to
tell Danny something important, he invites Reuven over to his house and addresses
Reuven, but he is really talking to Danny. Reuven finds this bizarre, but Reuven’s
father later explains to him that this method is rare in Judaism and part of the
mystical experience. He has chose to teach Danny with silence because he believes that
Danny must let the silence speak to him in order to better understand the suffering of
the people, so he can take on the suffering of the people when he becomes a rabbi and
takes his father's place. Danny eventually learns how to accept the silence and he even
embraces it. He tries to explain it to Reuven, but Reuven is not into the mystical side
of Judaism. In fact, Reuven's father repeatedly says he does not approve of
it.

It is not until the end of the novel, when Reb Saunders
accepts the fact that his son will not follow him and become a “tzaddik” (spiritual
leader) that Reb starts talking directly to Danny. There is a lot of interesting but
complicated Jewish history in this novel. The author does a good job of explaining most
of it, but it is helpful to do some research about Hasidic, Sephardic and
Ashkenazi Judaism to fully grasp what is going on in this
novel.