Acharya Prashant explains that the presence of ego determines whether one is truly a doer or a non-doer. A person with an ego is always performing actions even when they appear still, whereas a wise person without an ego remains a non-doer even while performing all actions. This state of non-doing is exemplified by Shri Krishna, who manages the entire universe without any personal desire or attachment to the results. The fundamental difference between a doer and a non-doer is that the doer acts to gain something significant to fill an inner void, while the non-doer acts playfully because they already possess the ultimate truth, the Atman. Spirituality does not teach inaction or frantic ambition; instead, it teaches 'right action,' which flows naturally like a river without the burden of the 'I' sense.