Who is Private Detective, Chanakya contribution to being a detective

Chanakya's contribution to being a Successful Private Detective
People have question comes in their mind that Who is Private Detective, how private detective work, Where did the Detectives come from. Detectives profession is the oldest profession in the world, and It first started in India. Acharya Chanakya’s introduce Private Detective Profession around 322 BC to India. In this video Private Detective Sanjeev Deswal explain the history of Detectives. He explain about the contribution of Chanakya to being this profession successful.
Why does society need Private Detectives like Profession where did this profession come from, how did it work, how do they work, what kind of tools or modes operandi do they use
as far as coming of this profession in India is concerned.