Explanation:

Shankara established the nature of Atman or soul as inert energy and proved that it is the same cosmic energy or Brahman. By getting rid off Jiva, who is the doer and enjoyer of all works and by attaining the soul, one gets total peace by disassociating with all worldly affairs. This is called as the attainment of self by filtering the essence of Jiva, which is the inert energy or Atman. Since, Jiva is the work of Atman, leaving Jiva means only stopping the work of Atman as in the deep sleep. Thus, Atmayoga means attainment of deep sleep during the state of waking itself and therefore it is the attainment of peace in the waking state itself. This state is also needed for theists to do the divine service of God. This state is the final state for atheists where they enjoy the peace as bliss and treat soul as God. But the theists also enjoy the peace as peace and soul as soul in this state. Such attainment of peace is essential even for theists, who try to please God and achieve bliss from God. This Atmayoga is the final state for atheists and intermediate state for theists. The final degree of the school is common to a student, who stops there, and also for a student, who advances to college. The stopping student feels that it is the ultimate degree and the advancing student feels that it is an intermediate degree. This difference in their feelings has no relevance in doing efforts to attain the degree. Hence, the final degree of school is open to all and need not be specified for anyone of these students. For this reason, Shankara did not specify theists or atheists as relevant for His commentary, which establishes the Atmayoga. Shankara did not mention God beyond Atmayoga in His commentary, for the reason that the atheists will run away if such mention of God related to theists only is done in His commentary. Therefore, the commentary of Shankara is universal to all humanity irrespective of theists and atheists. The word Brahman satisfies both theists and atheists. For atheists, the cosmic energy is the ultimate God or Brahman. For atheists, the cosmic energy is the greatest item in the creation or Brahman. Since, Brahman can mean both God as well as greatest item in a category, the theists and atheists are not separated in using the word Brahman. Both are separated only in the sense of the word to be taken in relevance to their context.