Acharya Prashant explains that nature is not just external elements like rivers and mountains, but also includes our own intellect, memory, and brain. He clarifies that the brain and mind are distinct; the brain is purely natural and governed by fixed laws, much like the physical world. True consciousness is something else entirely and is not tied to the brain's biological functions. He emphasizes that humans are often driven by natural impulses like anger and aging, which they cannot control. A person who can remain untouched by these natural processes and emotions is defined as a 'Purusha', whereas others remain mere extensions of nature.