 The struggle and doubt of being torn between the belief in God's immanence and the very real sensual experience of the indifferent world is a key theme in the movement's literature.Many tracts have been devoted to the subject, acknowledging that the "callous and rude" flesh hinders one from holding fast to the ideal, and these shortcomings are extremely hard to overcome even in the purely intellectual level, a fortiori in actual life.Another implication of this dualism is the notion of "Worship through Corporeality", "Avodah be-Gashmi'yut".