Actions determine the course of the Intellect. In the actions performed by a person, there are two types : the proper and the improper. Man's intellectual tendencies depend on the nature of his actions, good or bad. Bad actions pollute the intellect. Good deeds purify the intellect. Hence, the condition of the intellect is determined by one's actions.
(Sanathana Sarathi, Arpil 1997, pg 92)