"God is merely a man-made concept because all  notions of God are inherently created by humans." 

This line of reasoning is inherently circular,  as it employs the premise of God's concept being  

human-generated as proof of its artificiality.  The argument essentially concludes that God  

is a man-made construct on the basis that  concepts of God originate from human thought. 

However, this reasoning is circular  because it assumes what it seeks to prove:  

the premise that all ideas of God are human  creations is used to substantiate the conclusion  

that God, therefore, is a fabricated concept. This approach neglects to consider the possibility  

of a divine entity existing independently of  human conceptualization, presupposing instead  

that the very act of human conception of God  invalidates the existence of a divine being. 

Such an argument fails to provide  external verification for its claim