Metamath Proof Explorer
		
		
		
		Description:  The base set of a monoid is not empty.  Statement in Lang p. 3.
       (Contributed by AV, 29-Dec-2023)
		
			
				
					|  |  | Ref | Expression | 
					
						|  | Hypothesis | mndbn0.b |  | 
				
					|  | Assertion | mndbn0 |  | 
			
		
		
			
				Proof
				
					
						| Step | Hyp | Ref | Expression | 
						
							| 1 |  | mndbn0.b |  | 
						
							| 2 |  | eqid |  | 
						
							| 3 | 1 2 | mndidcl |  | 
						
							| 4 | 3 | ne0d |  |