It is the reason something exist for example if you ask what the purpose of a car is you would say its purpose is to get me from one place to another.
Answer:
The way he writes isn't as modern as today's way of speaking so most people have struggle understanding because they grew up speaking modern terms.
Explanation:
To determine the central idea of an essay on man, the reader should first FIND OUT THE SUBJECT OF THE ESSAY AND WHAT THE AUTHOR OVERALL OPINION ABOUT THE SUBJECT IS.