How can a person reach a state of joy solely from within himself without relying on external stimuli?
One way for him to achieve true joy is to “contemplate and visualize with his mind and his understanding the concept of God’s true unity.”
Just as a person must dwell on certain ideas in order to elicit painful feelings, so must he contemplate the concept of God’s divine oneness and unity in order to elicit joy.
In order for a persons thoughts to lead to knowledge that is not only theoretical but will change his life, he must direct his thoughts.
Directing one’s thoughts involves a process of careful analysis whereby a person approaches a concept from multiple angles.
In this way, he visualizes the concept in his imagination as tangibly as possible so that his soul can connect itself to that concept fully, both intellectually and emotionally.
Rabbi Adin Steinsaltz