The level of a soul is not related to a person’s intellectual proficiency, nor to any other physical or spiritual ability. It is based on one factor only: the soul’s sensitivity to holiness.
The more sensitive to holiness the soul is, the higher its source.
The higher the source of the soul, the deeper and more natural its sensitivity to holiness and to God’s presence, and the less illumination and awakening it requires from the outside, because it is drawn to attain this of its own accord.
Conversely, when a person possesses a lowly soul, his basic sensitivity to holiness is limited, and it is more difficult for him, perhaps even impossible, to achieve a spiritual awakening, even one that is only in his thought and mind.
Rabbi Adin Steinsaltz