Acharya Prashant explains that the definition of yoga depends on one's self-identification. If a person identifies solely as a physical body, then yoga remains a physical practice. However, if one recognizes that their primary concerns and restlessness are mental, then yoga must address the mind. While physical yoga or Hatha yoga is appropriate for bodily ailments like a sore knee, the speaker argues that the primary suffering of modern mankind in the 21st century is mental rather than physical. He emphasizes that the mind is currently unhealthy and restless, and therefore, the yoga needed today is the yoga of the mind. He clarifies that while yoga literally means union, it is essential to understand what the mind truly desires to unite with. The mind is constantly seeking happiness and peace through material consumption, yet it remains unsatisfied. This blind consumption is leading to global crises such as species extinction and climate catastrophe. Acharya Prashant distinguishes the mind from the brain, noting that the brain is a physical organ concerned with security, while the mind is driven by deep-seated desires. He concludes that true yoga must be an inquiry into who we are and what we truly want, as material consumption can never provide the final peace the mind seeks.